High-level bank regulators were aware of and in some cases even directed thrifts to inappropriately backdate capital contributions, according to a report released on Thursday by the U.S. Treasury Department watchdog.

The Treasury's Office of Inspector General report said it was alarming that high-level officials at the U.S. Office of Thrift Supervision approved or directed the backdating of capital at six thrifts, including failed lender IndyMac Bank.

In March, the inspector general placed acting OTS director Scott Polakoff on leave pending a review. The OTS, which largely regulates mortgage lenders, is an agency within the Treasury Department.

(Reporting by Karey Wutkowski and John Poirier)