Mr. Thornburgh, an ex- governor of Pennsylvania, was appointed in 2002 to investigate the WorldCom fraud.

"The failure of the Oklahoma attorney general to inform federal officials, who had been actively investigating the WorldCom fraud, runs the risk of undermining the federal prosecutions," he said.

The WorldCom fraud follows scandals at energy giant Enron and its auditor, Andersen.

Citigroup had never produced the materials supporting these claims to Richard Thornburgh, the examiner appointed by the bankruptcy court to investigate the WorldCom fraud, the brief stated.

One thing the WorldCom fraud shows is the value of a fresh set of eyes on the books.

The WorldCom fraud is far bigger in money terms than Enron's misdeeds, and will further undermine the trust of investors in corporate America.

Cooper's book about her life and the WorldCom fraud, Extraordinary Circumstances: The Journey of a Corporate Whistleblower, was published in 2008.

Prosecutors have asked the judge overseeing the case to sentence Mr. Ebbers to 85 years for masterminding the $11 billion WorldCom fraud, the largest in United States corporate history.

That S.E.C. suit was filed in federal court on the same day that a jury convicted Mr. Ebbers in the WorldCom fraud.

There were no documents tying Mr. Ebbers to the WorldCom fraud, but his claim of ignorant innocence was not believed by jurors.