Wal-Mart Stores, responding to criticism that it has failed to provide adequate health benefits, said yesterday it will expand coverage for workers and open more than 50 health clinics in its stores.

The world’s largest retailer will allow more workers to become eligible for the lowest cost health plan, cut the waiting period for part-timers, and allow their children to be covered.

Wal-Mart will more than quadruple the number of clinics this year after opening nine in Arkansas, Oklahoma, Florida, and Indiana last year.

The company’s chief executive, H. Lee Scott, also called for lawmakers to work with companies on the rising cost of health care. The initiatives come a month after Maryland became the first state to legally require large companies to pay a set amount for employee health care benefits, a measure that states including California are seeking to adopt.

“It’s either an olive branch to acknowledge that they need to do more or others might view it as throwing down the gauntlet for government and business to work together,” said Don Gher, chief investment officer at Bellevue, Wash.-based Coldstream Capital Management, which holds Wal-Mart shares among $900 million in assets. “Are there going to be additional costs? Certainly.”

Labor groups, American lawmakers, and advocacy organizations including Wal-Mart Watch have criticized the company’s pay and benefits, saying the offering is so poor that many Wal-Mart workers are on public assistance programs including Medicaid.

According to a Wal-Mart memo, 5% of the company’s workers are on Medicaid and 19% are uninsured. The company had more than $300 billion in revenue last year.

Wal-Mart, the country’s largest private employer with 1.3 million employees, said it will expand the availability of the lowest cost “Value Plan” health benefit to at least half of all associates. The option costs $11 a month for individuals and 30 cents more a day for children, the company said yesterday.

As he called for government and corporate America to work together on rising health care costs, Mr. Scott said yesterday that during its most recent enrollment period the company signed up 70,000 associates who didn’t have Wal-Mart’s health insurance.

More than half of them were previously uninsured, he said.

“The soaring cost of health care in America cannot be sustained over the long term by any business that offers health benefits to its employees,” Mr. Scott said in the statement. “We have to solve the health care challenges facing America. We have to do it together. And we have to start now.”

Mr. Scott will discuss health benefits issues Sunday during a speech at the National Governors Association winter meeting in Washington, the company said.

Wal-Mart’s plans and Mr. Scott’s speech may reflect a renewed effort on the company to try to boost its image. In November, the New York Times reported that Wal-Mart had hired former presidential advisers Michael Deaver and Leslie Dach to handle some public relations matters. Mr. Deaver worked for President Reagan and Mr. Dach for President Clinton.

Shares of Bentonville, Ark.-based Wal-Mart rose 22 cents to $45.70 at 4:01 p.m. in New York Stock Exchange composite trading. They have declined 2.4% this year after falling 11% last year.

Last month, Maryland passed a law that requires companies with more than 10,000 workers to devote at least 8% of their payroll to health care. Wal-Mart employs almost 17,000 people in Maryland.

A California bill, introduced by a Democratic state senator, Carole Migden, would also require companies with 10,000 or more workers to spend at least 8% of their total wages on health care or reimburse California’s state-run medical program by a similar amount.

Efforts to pass similar laws faltered in states including Washington, Indiana, and Wisconsin this year. A group representing Wal-Mart and other “big box” retailers this month challenged the law in Maryland. The company on January 1 introduced a new health plan that costs some employees as much as $23 a month. In some markets, it costs about $11 a month.