The lawsuit marks the latest fallout for the FDIC from three bank failures earlier this year that cost the agency's deposit insurance fund about $32 billion and have drawn scrutiny by lawmakers.

The lawsuit was filed on Dec. 5 in the U.S. District Court for the Northern District of California but has not been previously reported.

With assets of more than $200 billion, First Republic in May became the largest bank to fail since the 2007-2009 global financial crisis, despite efforts by major banks including JPMorgan Chase & Co to right the ship, including a $30 billion infusion of deposits in March of this year.

As receiver, the FDIC in May sold virtually all the bank's assets to JP Morgan, which assumed all deposits as well.

In their complaint, the former employees allege that in mid-May the FDIC ceased paying into a deferred compensation plan that First Republic had earlier established for them in a trust. They say the FDIC instead began treating them as unsecured creditors, meaning they could be left with nothing.

"It's really inequitable. The employees are the ones that kept the bank healthy and profitable," said attorney Timothy Walsh of Winston & Strawn. His clients did not include any of the top executives whose alleged mismanagement contributed to First Republic's demise, Walsh added.

"They should not be penalized in this process."

Walsh said the FDIC's resolution of First Republic protected the Wall Street banks that injected deposits, while the former employees' retirement funds were much smaller. First Republic's failure cost the FDIC about $15 billion, according to a recent estimate.

The FDIC is also facing litigation from the former parent company of Silicon Valley Bank, which is seeking the return of about $2 billion the agency seized after the bank's collapse.

The FDIC declined to comment. JPMorgan did not respond to a request for comment.

(Reporting by Douglas Gillison; Editing by Bill Berkrot)

By Douglas Gillison