Wal-Mart Stores Inc., under fire from critics who say it doesn’t pay enough, said it will raise the starting pay rates for almost a third of its American Wal-Mart and Sam’s Club stores.

The world’s largest retailer said it also will boost performance-based pay. Minimum starting pay will rise an average of 6% at 1,200 stores, spokesman John Simley said yesterday.

Wal-Mart pays full-time employees an average of $10.11 an hour, compared with $17 at Costco Wholesale Corp., the largest U.S. warehouse-club retailer.

Labor and religious groups have criticized Wal-Mart’s wages and benefits, and the company faces legislative attempts to regulate what it pays. Wal-Mart is raising its pay as Congress debates whether to increase the federal minimum wage 41% to $7.25 from the current $5.15.

“Wal-Mart is helping itself as much as helping employees,” said Burt Flickinger, managing director of Strategic Resource Group, a New York consulting firm. “There was disparity versus competing retailers like Costco, like others in the food and drug sector.”

Chicago last month passed a living-wage bill a week after a federal judge in Maryland overturned a law that required the retailer to spend 8 percent of its payroll on health care. The Chicago law requires workers at stores larger than 90,000 square feet to pay at least $9.25 an hour plus $1.50 in benefits.