The US Department of Justice has charged three British bankers with involvement in a fraudulent investment scheme involving failed energy giant Enron.

As these charges demonstrate, our investigation into the collapse of Enron Corporation is active and ongoing

Larry Thompson Deputy Attorney General

The three men worked for National Westminster Bank and allegedly made secret investments in an Enron front company, diverting proceeds amounting to $7.3m.

Enron filed for bankruptcy last December, after a collapse which has led to a series of investigations and a guilty verdict against Andersen, the company's auditor, for obstructing justice by shredding evidence relating to Enron's accounts.

These charges are the first which directly involve Enron, and sources close to the investigation speculate that the government hopes the three bankers might provide vital evidence against senior Enron officials, in return for clemency in their own case.

"As these charges demonstrate, our investigation into the collapse of Enron Corporation is active and ongoing," said Deputy Attorney General Larry Thompson.

Greenwich NatWest is now part of Royal Bank of Scotland and a spokesman said: "Naturally, we will monitor the criminal proceedings carefully and will continue to co-operate with the with the appropriate authorities involved in the Enron investigation."

Back in UK

Gary Mulgrew, 40, Giles Darby, 40, and David Bermingham, 39, have all been charged with wire fraud.

The charges were filed in Houston, where Enron had its headquarters, although the three suspects are currently believed to be in the UK.

They were employees of Greenwich NatWest, a division of the National Westminster Bank, based in Greenwich, Connecticut.

They are accused of secretly investing in an Enron entity, Southampton LP.

Investigators say the same kind of methods were used by Enron executives to illegally inflate investments.

NatWest was one of a small group of banks that did the most business with Enron, and so were accorded special treatment by the energy giant.

The Justice Department alleges that the three men recommended an interest held by NatWest in an Enron-related partnership be sold for $1m, while planning with Enron executives to purchase the interest themselves for �250,000.

Then, only weeks later, they liquidated it for more than $7.3m, according to the charge.