(Reuters) - Bank of America Corp asked a judge to disqualify the law firm representing AIG in the insurance company's $10 billion mortgage-fraud lawsuit against the bank, alleging a conflict of interest by one of the firm's partners.

Bank of America, in a court filing, said the lawyer previously defended Merrill Lynch & Co and First Franklin Financial Corp, both now owned by the bank, against allegations that they made and sold defective mortgage loans.

The lawyer is Marc Becker, a London-based partner at Quinn Emanuel Urquhart & Sullivan. He is no longer working on the American International Group Inc case following Bank of America's objections, the bank said in the filing, made late on Monday.

"Becker's involvement in this case has already tainted these proceedings," wrote Marc Dworsky, a partner at Munger, Tolles & Olson, which represents Bank of America and previously employed Becker. "Quinn cannot be in a position to use defendants' confidential information against them in the future -- particularly in a case of this magnitude."

The bank said the law firm should be disqualified because the AIG case raises allegations similar to those in the Merrill and First Franklin cases. It said Becker's earlier involvement in the AIG case is a "flouting of the ethical rules."

Calls to Becker and another Quinn Emanuel partner working on the case were not immediately returned on Tuesday.

AIG, in its lawsuit, accuses Bank of America and its Countrywide and Merrill Lynch units of misrepresenting the quality of more than $28 billion of mortgage-backed securities bought by the insurance company, and lying to credit rating agencies about the underlying loans.

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.

(Reporting by Jonathan Stempel in New York; editing by John Wallace)