“Quinn cannot be in a position to use defendants' confidential information against them in the future — particularly in a case of this magnitude,” Dworsky added.

The challenge raises the stakes in one of the biggest lawsuits stemming from the global financial and credit crises.

AIG obtained $182.3 billion of federal bailout and remains owned largely by taxpayers. It accused Bank of America and its Countrywide and Merrill units of misrepresenting the quality of about $28 billion of mortgage-backed securities it bought, and lying to credit-rating agencies about the underlying loans.

Gregory Joseph, a lawyer for Quinn Emanuel, in an email called Bank of America's motion a tactical effort to remove the firm from the case. The firm is one of the largest specialists in mortgage-securities litigation.

“They know perfectly well that he would not share any confidential information, and he never did,” Joseph said, referring to Becker. “Its motion never even addresses the governing standard — whether there is any risk of trial taint — because of course there isn't.”

AIG spokesman Mark Herr called the Bank of America motion “simply an attempt to distract from the merits of the case.”

CONFLICT?

James Cohen, a Fordham University law professor and legal ethics specialist, said Becker's earlier work likely did not warrant Quinn Emanuel's disqualification from the AIG case.

“I don't think there is a conflict,” he said. “They are unrelated matters and his representation of Merrill and First Franklin is more than two years in the past. The mere claim that a lawyer developed a strategy for defending this kind of lawsuit does not mean the lawsuits are significantly related.”

Cohen said it could prove “problematic” if presiding judge Barbara Jones decided Becker was not screened fast enough, but that an effective screen could address this issue.

He added: “It is of high value for a party to have the law firm of choice.”

Becker now works in London. He did not immediately return a call seeking a comment.

Quinn Emanuel's other cases include most of the 18 Federal Housing Finance Agency lawsuits against Bank of America, other banks and at least 131 individuals to recover losses on $200 billion of soured mortgage debt held by Fannie Mae and Freddie Mac .

The FHFA is the conservator for the mortgage financiers.

The case is American International Group Inc v. Bank of America Corp et al, U.S. District Court, Southern District of New York, No. 11-06212.