WASHINGTON, Aug. 30 — The Justice Department’s internal watchdog disclosed today that he was investigating whether sworn statements to Congress by Attorney General Alberto R. Gonzales were “intentionally false, misleading or inappropriate.”

The first official confirmation that Mr. Gonzales is under investigation within the executive branch over the truthfulness of his testimony came in a letter to the Senate Judiciary Committee from Glenn A. Fine, the inspector general at the Justice Department. The committee’s chairman, Senator Patrick J. Leahy, Democrat of Vermont, had requested the inquiry earlier this month.

For weeks, lawmakers from both parties have questioned whether Mr. Gonzales told the truth in sworn statements to Congress on a number of issues, including his involvement in efforts to preserve the National Security Agency’s policy of wiretapping without warrants, as well as his role in last year’s dismissals of several United States attorneys for what appeared to be political reasons.

It was not clear if the investigation by the inspector general was tied in any way to Mr. Gonzales’s announcement on Monday that he was resigning from the Justice Department, effective next month. He has offered no details for the reasoning behind his resignation or its timing, and his departure caught top aides by surprise.