WASHINGTON — The top Republican on the House Financial Services Committee is demanding data on banks he suspects are being asked to take significant haircuts on loans they extended to subsidiaries of American International Group, now effectively a ward of the state.

“While foreign and domestic counterparties were made whole, AIG has been attempting to force many of its creditors that are U.S. banks to accept severe reductions in the debt owed to them,” Rep. Spencer Bachus (R., Ala.) wrote in a letter to Treasury Secretary Timothy Geithner this week.

At least 17 banks are being asked to accept less than what is owed to them, Mr. Bachus said in an interview, citing information he has received.

“It’s tremendously unfair. What is it about a [credit default swap] that makes it any more sacred?” Mr. Bachus asked. “The credit default swaps were a bet … gamble … a risk.”

In an earlier letter to Mr. Geithner, Mr. Bachus said one AIG subsidiary, AIG Baker, was demanding a 72% reduction in principal on a $45 million syndicated loan made by a trio of unnamed U.S. banks. AIG Baker is an Alabama-based developer of shopping centers with a presence in about 20 states.

Mr. Bachus now is requesting details on banks providing credit to AIG and any of its real estate subsidiaries that have received federal assistance. Further, he wants to know the amount of the banks’ exposure to AIG, the names of all AIG subsidiaries that had relationships with small regional banks and the extent to which AIG has met its obligations to U.S. bank creditors.

The Treasury on Tuesday declined to comment on Mr. Bachus’s request.

The Treasury has been facing growing anger on Capitol Hill in recent weeks after the emergence of an oversight report that confirms the government failed to negotiate the best possible deal for taxpayers in connection with its $180 billion bailout package for AIG.

The report, from a special inspector general overseeing the rescue of AIG and other firms, suggests the Treasury and the New York Fed — headed by Mr. Geithner at the time — could have pressed AIG counterparties harder to accept less than the full amount they were owed in connection with credit default swaps written by the firm.

The report showed the government negotiated with AIG counterparties for only two days, stressing that taking haircuts on their positions was voluntary.

AIG counterparties paid in full include Goldman Sachs, Societe Generale and Deutsche Bank.

“They could have paid the regional and community banks for the amount of money they gave to any one of those institutions,” Mr. Bachus said.