He said evidence indicated that the fraud involved "people at a very high level" in the bank.
At the start of the 1990s, fraud involving cigarette smuggling was found to be big business.
The class action filed late Friday brings new accusations of fraud involving the partnerships.
"But the fraud you're looking into involves cutting corners."
Ten times in six years, we have referred cases of alleged fraud involving Commission employees to the judicial authorities.
Since fraud can involve a wide range of circumstances, it is difficult to provide general guidelines on how to pursue criminal charges in these issues.
The latest fraud involves an official who earned her clients millions illegally but apparently took no money herself.
In the same period, she says, there have been numerous allegations of fraud involving absentee ballots.
The contract also figures in the Justice Department's investigation into fraud involving military contracts.
He said the case was believed to be the largest fraud ever uncovered involving postage meters.