WASHINGTON — The Treasury Department’s inspector general has threatened to punish JPMorgan Chase & Co. for failing to turn over documents to regulators investigating the bank’s ties to Bernard Madoff ’s Ponzi scheme.

Inspector General Eric Thorson gave the largest U.S. bank a Friday deadline to cooperate with the Office of the Comptroller of the Currency investigation or risk sanctions for impeding the agency’s oversight. JPMorgan, according to the Dec. 21 letter, contends the information is protected by attorney-client privilege.

Thorson’s letter didn’t spell out what documents the Office of the Comptroller of the Currency is seeking or the focus of its investigation. Madoff is serving a 150-year sentence after confessing to the fraud that once claimed to have $65 billion in customer assets.

The previously undisclosed investigation adds to the lender’s troubles in Washington, where several agencies and lawmakers are investigating the bank’s loss of at least $6.2 billion on botched derivatives trades. The losses have prompted regulators including the Federal Reserve to consider tightening proposed restrictions on proprietary trading.

Business, Pages 26 on 01/05/2013