Treasury disputed the panel's findings. Department spokesman Andrew Williams said the estimates are based on assumptions, so they may be higher or lower than the actual market prices of the warrants. "For that reason Treasury is using a more comprehensive approach to valuing the warrants," including obtaining quotes from investors who buy and sell similar securities, he wrote in a statement.

As evidence, Williams pointed JPMorgan's decision to let Treasury sell its warrants at auction — an indication the bank thought Treasury was asking for too much.

"We've taken this action, which is consistent with Treasury's process ... and which allows Treasury to find the true market price," said JPMorgan spokesman Joseph Evangelisti.

Banks have been eager to exit the bailout quickly to avoid the stigma and exempt themselves from restrictions, including limits on executive compensation. Repurchasing the warrants is a necessary step, but has been challenging because of disagreement about the prices.

The oversight panel's analysis was reviewed by three finance professors from Harvard Business School. The panel is headed by Harvard Law School professor Elizabeth Warren. She was the first to propose a new consumer protection agency for financial products, which has become a cornerstone of the Obama administration's reform efforts.

One of the group's Republicans, Texas Rep. Jeb Hensarling, warned against interpreting the report as critical of Treasury's approach to the warrants.

"It is exceedingly difficult to predict the value of financial securities and time the markets over the short term much less the 10-year term of the TARP warrants," he wrote.