Retailers assail credit card fees in House hearing

Banks that issue cards, meanwhile, have reduced rewards and increased consumer fees, the GAO said.

"There are lessons here for the broader interchange debate," said Kenneth Clayton, a senior vice president at the American Bankers Association. "Intervening in this properly functioning market ... will hurt consumers."

Lawmakers were mostly noncommittal during the hearing, though some expressed reservations about the legislation.

"This is a very ill-advised bill," said Rep. James Sensenbrenner, R-Wis. "I think the current situation is a big plus for consumers ... and small business operators."

Visa executives have also complained that the bill, which applies only to companies with "substantial market power," wouldn't affect American Express Co. or Discover Financial Services.

The legislation was sponsored by Reps. John Conyers, D-Mich., and Chris Cannon, R-Utah.