The City Council is expected to pass a bill today that would require most large grocery stores in the five boroughs to pay at least some medical-insurance premiums for their employees.

The legislation, one of the first of its kind in the country, is a “pilot program” that would only apply to the one industry and to “big-box” stores that sell food.

The council, made up largely of pro-union Democrats, has blocked one of big-box store, Wal-Mart, from opening in the city and has condemned the retail giant, saying it mistreats its employees elsewhere in the country.

Council members said the Health Care Security Act will protect roughly 6,000 low-paid employees, at stores such as Gourmet Garage and Garden of Eden, and help to chip away at the number of city residents without medical coverage.

“It acts as a protection for low-paid workers and is also a protection for taxpayers, because there is no reason why we as taxpayers through our public health programs should have to pay the insurance of companies that don’t want to take the cost out of their profit,” Council Member Christine Quinn, a Manhattan Democrat who is the lead sponsor of the bills, said.

The bill, which with 42 co-sponsors is immune to the veto expected from Mayor Bloomberg, is a watered-down version of a measure that would have applied to a host of other industries.

It requires grocers who operate stores that are at least 10,000 square feet and have 35 employees to pay a “prevailing health care expenditure rate” for its employees. That rate is between $2.50 and $3.00 an hour for each employee and is pegged to the average amount paid by city grocers who already provide health insurance coverage for their employees, council officials said. Grocers that don’t comply will be subject to fines. Though the bill has the backing of several nonprofit groups, critics, including the Bloomberg administration said it violates federal law.

“The bill violates federal law, is riddled with loopholes, and providing health care to a selective group who works only in one industry is terrible public policy,” a spokesman for the mayor, Jordan Barowitz, said.

A representative of Wal-Mart said yesterday that it would be premature for the chain to comment on the legislation since it has no stores in the city at this time. Wal-Mart officials have said, however, that the stores provide competitive wages and benefits.

The council is also scheduled to pass several other bills today, including one that increases fines for stores that lock in employees on overnight shifts – another practice ascribed to some Wal-Mart stores.

Council Member David Yassky, the Brooklyn Democrat who sponsored the lock-in bill, is also introducing legislation to crack down on medical clinics that file fraudulent claims with auto-insurance companies.

The president of Brooklyn, Marty Markowitz, said the borough’s car owners pay some of the highest automobile insurance rates in the nation.

“Find an honest living instead of ripping off honest and hardworking motorists in Brooklyn and in New York City!” Mr. Markowitz said.