Bank of America (BoA) has filed a motion to disqualify US law firm Quinn Emanuel Urquhart & Sullivan from representing AIG in a $10bn (£6.3bn) securities litigation case, reports The Am Law Litigation Daily.

The bank argues that Quinn Emanuel is conflicted because Marc Becker, a London partner the firm recruited in 2009, had previously represented Merrill Lynch and a subsidiary as a partner at Munger Tolles & Olson, BoA's lawyers.

Becker joined Quinn Emanuel's London office after it opened for business in in the City in October 2008.

BoA asserts that before leaving his former firm, California's Munger Tolles, Becker had provided representation to Merrill Lynch and a subsidiary, First Franklin Financial, as part of the firm's work beginning in early 2008 advising on potential claims by mortgage-backed securities purchasers. According to BoA's motion, Becker billed more than 120 hours at Munger looking into Merrill's underwriting practices.

BoA claims it discovered Becker's alleged conflict on 8 September, a few months after Munger Tolles signed on to represent the bank. After BoA first raised the issue, Quinn Emanuel founder John Quinn sent the bank's lawyers an email on 20 September claiming that Becker "has had and will have nothing to do with this case."

However, in a 5 October letter, Quinn Emanuel's counsel Gregory Joseph acknowledged that Becker had reviewed a draft of AIG's complaint and later edited a motion to remand the case back to New York state court. Joseph also acknowledged that Quinn had not taken any affirmative action to screen Becker's involvement until BoA voiced its concerns.

Joseph's letter nevertheless asserts that Becker "is not, and never was, a member of the Quinn Emanuel team on the BoA action," that his work on the case spanned just 5.8 hours, and that he was never privy to confidential Merrill Lynch information during his days at Munger.

"Marc Becker practiced at Munger Tolles for 19 years as a highly respected and trusted associate and partner," Joseph said in his statement. "They know perfectly well that he would not share any confidential information, and he never did. This motion is simply tactical: BoA doesn't want to face Quinn Emanuel on the other side."

Both AIG and Joseph dismissed the notion that Quinn was conflicted in its representation. "The motion has no merit and is simply an attempt to distract from the merits of the case: that Bank of America sold AIG fraudulent residential mortgage-backed securities," said AIG spokesman Mark Herr.

Quinn Emanuel has turned to New York litigation lawyer Gregory Joseph as outside counsel. Joseph last year successfully went up against Quinn Emanuel and Morgan Stanley in defending Citigroup in a suit over a $245m (£155m) collateralised debt obligation.

The Am Law Litigation Daily is a US affiliate title of Legal Week.