"We live in a world of dark numbers, a place where you don't know all the facts," says the precise, clipped voice. Only the tiniest hint of passion creeps into the words. "There's a lot of institutions that play with these numbers, but even as of 1996, there was an estimated $6 trillion held offshore. Why, what's it doing there? Is the banking talent better in the Cayman Islands than London or New York? You pay a premium to go to these secret havens; you pay people to handle your money and you get less interest. So the question is: why?"

The tone is rhetorical and the voice pauses, letting the words hang in the air for a moment. Four men sit around the dark mahogany table, all but one with their shirt sleeves rolled up. This latter figure sits at the head of the group, a precisely turned out man, clasping his neatly trimmed fingers, temple-like, in front of him. "What are you buying for your premium?" he asks.

Martin Kenney is not an easy man to read, even when he is lecturing on his favourite subject: global fraud. He utters a somewhat odd, puffy laugh at the end of his sentences and peppers his conversation with Latin and legal phraseology. Yet speak with him for more than a few minutes, and it becomes quite clear that he is a driven individual. You might even say he was on some sort of crusade.

As one of the world's few truly global (multi-jurisdictional) lawyers, Canadian-born Kenney, 40, scours the globe for economic criminals. To Kenney's mind, the offshore world is being abused on a massive scale by these money launderers and white-collar criminals, people who have ripped off not just banks and corporations, but millions of average citizens - even countries in some cases. These fraudsters are Kenney's prey.

His company Interclaim, with its small team of 18 investigators, lawyers and accountants, travels where even few governments can tread. Tackling what they see as a multi-headed "hydra", they find and seize concealed criminal wealth on behalf of otherwise powerless victims. As such, Martin Kenney is probably the world's first global "fraud buster".

There is little clue to this economic war, standing in front of Interclaim's Georgian building on St Stephen's Green. Only the cold, mechanical gaze of the discreet security cameras, clinging to the faded brickwork, suggests otherwise. Past the huge, solid oak door and away from the sombre exterior, there is an undeniable buzz within. The work undertaken here is cutting edge; the atmosphere more Silicon Valley software house than traditional law firm.

And Interclaim is indeed a unique set up. When you read of rogue traders such as Nick Leeson, who brought down Barings Bank, or corrupt dictators siphoning millions into Swiss bank accounts, the chances are that Kenney's men could one day be on their trail.

The company was formed three years ago, following a New York dinner meeting between Kenney and Irving Cohen, 36, a sharp, direct Manhattan lawyer who became the company's first investor. They decided to locate in Dublin, because of its favourable tax breaks, proximity to London and many of the offshore banking jurisdictions in Europe, and the availability of high quality, young lawyers such as Orla McCoy, who calls Interclaim "extremely dynamic and challenging".

Kenney himself came from an old-school Canadian family. By his early 30s, this former champion ice hockey player - who is part of a consortium now planning to build a new ice-hockey and sports entertainment arena in Dublin - was already a high-flying partner in an international litigation firm and one of the world's few specialists in multi-jurisdictional law.

Yet it was the failure of traditional law enforcement agencies in tackling major economic criminals that really bugged Kenney - whom colleagues refer to as a "straightshooter" - and led to the idea for Interclaim. Only 17 per cent of institutional crime victims were taking civil proceedings to reclaim their money, according to a study by accountancy firm KPMG in 1994.

"Seventeen per cent!" Kenney, hands planted on his desk, says it again for effect. He utters his short, puffy laugh. "You know, in most normal communities, if a bank robbery takes place and someone has taken a gun and shot a teller, stolen money and run off down the street, people will help!"

Kenney explains that in the offshore world, it can be illegal even to ask questions about potential fraudsters, under harsh bank secrecy laws. Not to mention the fact, as Cohen adds, that economic criminals "tend to flit around the world in their own private jets, living in hotel suites", making it difficult and expensive for traditional law enforcement agencies to track them down. Financial restitution to victims is not high on the list of priorities either. Yet with up to $8 trillion - according to the latest estimates - travelling through this highly secretive world every year, including the proceeds of economic crime and the trade, the problem is clearly getting worse.

"There's a huge portion of the world's legitimate economy owned by nefarious criminals," says Kenney. "And it's very hard to distinguish between the legitimate economy and that which is not, because they have blended. How do you distinguish between the two?"

One of Kenney's senior sleuths, a former Scotland Yard detective called Richard Marston (who once brought to heel the entire banking system of a small Caribbean island), speaks in clear, desperate terms of the situation facing their team:

"The danger is in the power of the money these people [economic criminals] are able to accumulate - and then the purpose to which they may be able to apply that. The key to this is secrecy," he tells me in a soft, direct voice. "If you allow people to have secret assets, then you, as a responsible government, can never know what these people are doing with this money. They may be purchasing an atom bomb from one of the former Soviet states, who will sell them to the highest bidder. Or they may seek to destabilise your currency. You just don't know."

What Kenney decided to do, therefore, was quite different to what had gone before. Funded by a variety of private investors, Interclaim would work on a different premise to police and other agencies; it would hit the fraudsters where it hurt, in their pockets. How? The company would buy up "claims" - usually massive, unsolved frauds - for a fraction of their real value from the defrauded party. Or it would enter into a partnership with victims of economic crime, with whom it would then split the proceeds of successfully recovered funds (usually 50/50).

First, Interclaim makes extensive use of "gagged" (secret) court orders, to obtain documents or enter premises, just like a law enforcement agency. Coupled with this are months of painstaking surveillance and sting (undercover) operations to monitor and build intelligence about the target. Specialist accountants are brought in to trace document trails and build a model of how a crime was committed. Then a variety of lawyers and other specialists, such as handwriting analysts and IT specialists, are drafted to help the case. The end result is startling: Interclaim tracks down the fraudster's wealth and has his or her assets frozen, right across the globe, at exactly the same time. This innovative use of civil law has been found to catch fraudsters completely off guard, sometimes even forcing them into bankruptcy.

Kenney aims for a success rate of one in three cases - where the one successful case pays for the costs (and more) of the other two. And this in an area of law in which the traditional success rate is, at best, one in ten. The Interclaim model has been so successful that FBI has referred one of North America's most complex fraud cases to the company.

This case is the subject of a secret meeting called by Interclaim and discussed in coded language. As we file into Kenney's airy offices, with a grand view over the park opposite, Cohen insists I leave my tape recorder switched off. The mood is grave, business-like. "We've got another victim on Blair Down," Kenney says in his high, nasal tones. Eyes look up from the table. This is a complex battle involving close to a million victims. Interclaim has already sunk several million dollars into a series of legal clashes with the criminal, seizing some of Canada's most prominent pieces of real estate in the process (which, it alleges, has been purchased with victims' money). Months of painstaking surveillance and undercover work, as well as secret legal proceedings, have been invested in the case.

The target is James Blair Down, convicted felon and one-time real estate agent, who ran illegal telemarketing scams into the US from Canada until 1998. He promised his victims fantastic odds and winnings if they invested in his foreign lottery resale schemes - "investing" their money into a so-called pool of foreign lotteries. Instead, he disappeared with their cash, estimated to be $240 million. This was then laundered through a complex series of offshore constructs into assets around the world, out of the reach of police and the US civil courts.

Down's staff of 500 telemarketers operated from high pressure "boiler rooms", targeting and befriending vulnerable, elderly Americans, many of whom came to regard the callers as their friends (even though the sales staff often used crude pseudonyms such as Michael Jackson and George Michael). In fact all these "lottery sales" were illegal in the USA.

FBI Special Agent Ross Gaffney called Interclaim in 1998, after the agency had managed to retrieve just $12 million of the victims' money. Like most government agencies, the FBI simply didn't have the resources necessary to pursue this global case. To date, it had also traced just 900 victims. Down plea-bargained a six-month jail sentence (which he served last year) in return for the dropping of 144 other felony counts, including money laundering and racketeering. The victims were dying off and few knew where to turn.

"Our one-man marketing office on the east coast [of America] has thousands of letters from these victims," says Kenney. "These people were elderly and vulnerable and they thrived in a mid-20th century era which was very different from today's. We're talking about our grandparents and great-grandparents here."

"We've been contacted by the daughter of one lady who lost over $1 million and who has Alzheimer's," he tells the group, then turns to address me directly. "The daughter says that her mother was so fooled by these people that she would get all dressed up in her Sunday best on the nights that the lottery was being announced - because she would win the lottery, she was guaranteed to be a millionairess. She would phone caterers to bring platters of food, to welcome all the news broadcasters from television because she would be announced as this new lottery winner," his voice drops, "and of course, nobody called her. They just took her money."

"She actually had access to a million dollars of the family's money," says James McGunn, 55, a silver-haired giant who is Kenney's co-manager of investigations. He shakes his head. "And it was taken," Kenney adds, deadpan.

Later, in McGunn's office, I study surveillance pictures of Down. He's a heavy-set, moustachioed figure who appears to glance nervously around him. "You're talking about a huge case, involving hundreds of millions of dollars moved offshore," says McGunn in his rumbling baritone, surrounded by certificates from his days as a US Secret Service Agent. He jots down a quick note to speak to one of his informants. "To find that money involves tracing the activities of that individual, from different ends - finding out where the money went, and where it is now. These people don't write a cheque from the bank. Land is not in their name."

McGunn tells me that economic criminals have been known to use an armoured security van to physically move millions of dollars in cash from one bank to another across the street in order to break an electronic or document trail. "So you try and identify partners and business associates, business connections, any financial institution they're using. You determine who leased their vehicles, who lives at certain addresses, and tie it all together."

McGunn says such techniques were used to launch a series of raids against Down on January 29 last year, the day after he entered prison to serve his six month sentence. More than 110 people were assembled across the world for the raids - lawyers, videographers, interim receivers, security personnel, computer specialists and local law enforcement officials. The raids included 25 office buildings and commercial properties in Calgary, Canada, Down's own home, the homes of his legal and financial advisers in Vancouver, and a seaside mansion in Barbados. Irving Cohen later told me of the look of shock he saw etched on their faces, as the full magnitude of the raids took effect. Over $100 million of assets was seized and frozen, from real estate to racehorses.

McGunn's dry, business-like tone conceals the complexity of this task. Former intelligence operatives and private investigators were engaged to shadow Down for months. The chase took in Vancouver, Calgary, Washington, and places as far afield as the Caribbean, South America, Australia, Hong Kong and Papua New Guinea. Agents assembled in covert teams, often at short notice and in situations of considerable danger. They even befriended Down's brother, Tim.

The two sides are now engaged in a bitter struggle in the Canadian appeal courts where Interclaim has already invested some several million dollars. If it wins, it will return 50 per cent of the proceeds to the several hundred thousand victims it has identified to date. If it loses, all effective chance of regaining their money will be lost. Two large and influential US pressure groups, the American Association of Retired Persons (AARP) and Public Citizen, have put in motions to intervene in the appeals court in Canada on Interclaim's side. And at Interclaim's request, a class action was recently launched against Down. The law firm behind this action, Ness Motley, was featured in the recent Hollywood film, The Insider, about the tobacco industry.

In the meantime, the company has been working to trace other fortunes lost to creditors. It recently managed to collect a large debt owed by a company based in Montenegro for a London metals trader. Work in progress includes the pursuit of a multi-million dollar fraud linked to the bribing of a Florida bank official and a huge case involving abuse of power and corruption of foreign government officials.

As I prepare to leave, Kenney is clearly fired up about the effects of such cases on the victims: "I've had a banker have a heart attack, seen others lose careers. People lose their edge, they lose their confidence," he says, "because they've been tricked and lost faith in themselves. It's like rape. It's that kind of violation."

He paces on the Persian carpet: "You know, I've seen victims - an elderly couple who lost $52 million and are now living in a trailer in Florida - that can't pay a phone bill. They had $52 million and the fraudster took it all, picked them clean."

Although he refers to his battles as a "grand play", there is a barely concealed loathing in Kenney's voice when he talks of the fraudsters: to him, they seem sociopathic, not lovable rogues who do little harm except to bloated financial institutions.

"They're as sophisticated and bright and as well organised and articulate as some of the best commercial business people in the world could ever be. And some of these fellows are really sick! They get their jollies off of victimising and laughing at people. Why do they do this? Well, there's a sickness there; they have sick, psychological states of mind."

This vision has brought Kenney his critics. Robert Millar, one of Blair Down's Vancouver lawyers, has said that his client was "blitzkrieged" into submission by Interclaim. "I don't like what they do. It may be novel and ingenious, but it's wrong." Another member of his team called them "international economic terrorists who practise extortion."

Others, however, have nothing but praise. "We find ourselves very much frustrated by our inability to help victims," says John Moscow, assistant district attorney in the Office of the New York County District Attorney. "We have no horses to pursue assets: we often get the criminal but not the money," which is where Interclaim comes in, he believes.

Martin Grieves, a principal financial investigator with Britain's Serious Fraud Office, adds: "I think we've got a moral duty to recover the citizens' money, whether you consider them to be high-worth mugs who were simply greedy, or whether they were purely duped. We should be able to do something as far as the money is concerned - because, unless we can take away the money from the criminal, we're not removing the deterrent. And it's a serious problem."

With the evening drawing in, and the Dublin nightlife about to begin, Kenney himself is circumspect. "You know, we're only a small part of the opposing force," he says, sweeping up his briefcase. "There's probably room for another five or six Interclaims out there, easily. Ten years ago, what we do was almost unheard of. Now there's tens of billions of dollars stolen every year by fraudsters - and that's probably a conservative figure. I tell you, if, figuratively speaking, we vanquish some of these swindlers, that will mean more to our victims than any cheque."

The Scale of Economic Crime

The scale of economic crime and money laundering is staggering; according to a recent report in the International Herald Tribune, up to $8 trillion now passes through offshore jurisdictions. No-one knows how much of this is illicit, because secrecy laws in many of these jurisdictions make it a crime to ask. For example, the government web site of the tiny Caribbean island of Antigua tries to attract offshore investors by bragging that it is bucking the trend "toward greater disclosure" of financial information. "The emphasis on non-disclosure provides a high comfort level," it says.

Anguilla's web site says companies can incorporate there in just 24 hours, while Dominica boasts of the "absence of tax treaties or exchange agreements with any other country."

The Cayman Islands has just 30,000 citizens, yet nearly 600 banks - making it the fifth largest banking centre in the world. Bigger than Chicago, Rome, Frankfurt, Paris, Los Angeles and Dallas. Many of its banks exist simply on paper. One senior US official has said that some of these small countries, which offer both strict banking secrecy and an easy change of identities, are creating "one-stop shopping" for criminals.

Investigators are already looking into how $7 billion of International Monetary Fund (IMF) loans was apparently laundered from Russia via the Bank of New York. The investigation has prompted the Russian government and presidency to angrily deny any involvement. In Russia, almost 100 bankers have been murdered during the past five years, which police believe is a direct result of organised crime and money laundering. Investigations can reach the highest level; Indonesia's former President Suharto was, until recently, under suspicion of laundering billions of dollars out of his country.

It is hard to comprehend how even one individual, let alone a gang, can cause such a problem: disgraced broker Martin Frankel, who was recently arrested in Germany and handed over to the FBI, is suspected of swindling $200 million or more of his clients' money.

"Money laundering is no longer considered something that a bunch of thugs on a street corner are doing with some drug money," says Interclaim's Richard Levinson. Irving Cohen adds: "You can get a nominee director of a corporation for about $1000 in a dialup company. Another person pretends to be the owner of this corporation for a $500 service fee. They open a bank account for that company and the first person is then the technical owner. The only risk you take is if they steal from you or rip you off."

According to Martin Kenney, in the large fraud cases there may be four or five separate self-contained entities, each perhaps with 250 corporations, all owning parts of each other and then owned by a trust with secret beneficiaries. And the name of those beneficiaries is locked in a safe in a lawyers office in the Bahamas. "It becomes an enormous task to unravel it. It's a multi-headed hydra."