WASHINGTON – Federal bank regulators have sued three former top executives of Washington Mutual, the biggest U.S. bank ever to fail, accusing them of negligence in allowing risky mortgage lending. The civil suit seeks $900 million in damages.

The Federal Deposit Insurance Corp. filed the suit Wednesday against former WaMu CEO Kerry Killinger, ex-Chief Operating Officer Stephen Rotella and David Schneider, who headed the bank’s home loans division.

The FDIC said the three executives pushed for expansion of WaMu’s risky lending even though they knew or should have known that its loan standards and controls were inadequate. The bank collapsed in September 2008 and was sold for $1.9 billion to JPMorgan Chase in a deal brokered by the FDIC.

Killinger, Rotella and Schneider adopted imprudent lending policies and caused the bank to make home loans “with little or no regard for borrowers’ ability to repay them,” the FDIC alleged.

The suit was the FDIC’s most high-profile legal action so far seeking to recover losses from banks that failed during the financial crisis.

An investigation by a Senate subcommittee into Seattle-based WaMu’s collapse found that its lending operations were rife with misconduct, including fabricated loan documents. It also concluded that management failed to stem the deception despite internal probes.