The private equity firm that owned a controlling interest in failed commodities brokerage Refco Inc. has filed a $245 million lawsuit against Mayer, Brown, Rowe & Maw, accusing the law firm of helping to conceal the sham transactions that led to Refco’s collapse.

Boston-based buyout firm Thomas H. Lee Partners filed a 50-page complaint against Mayer Brown on July 26 in federal court in Manhattan (07 Civ. 6767). In the suit, Lee said Mayer Brown handled 17 fraudulent transactions at the behest of Refco’s executives between 2000 and 2005.