Giant Food LLC and the union that represents local grocery store employees are pushing for an ordinance aimed at keeping Wal-Mart supercenters out of Montgomery County.

Wal-Mart has no supercenters in the county and says it has no plans to build one.

Giant and United Food and Commercial Workers (UFCW) Local 400 are prime advocates of the proposal before the Montgomery County Council. The measure sponsored by County Executive Douglas M. Duncan would impose tough new zoning restrictions on stores that are larger than 120,000 square feet and devote at least 10 percent of their floor space to groceries.

That defines the typical Wal-Mart supercenter, a retail behemoth that carries everything from gas grills and flat-screenTVs to produce and deli meats. Across the country, the nonunion discount stores have been a serious competitive threat to established supermarkets with their unionized workforces.

Although other Washington area jurisdictions have imposed restrictions on "big box" stores, the proposal in Montgomery County is aimed more narrowly at Wal-Mart.

It would exempt stores that do not sell food, such as most Target stores and Home Depot, and it would exempt club membership stores such as Costco.

Wal-Mart, which is based in Bentonville, Ark., has 14 of its standard discount stores and six Sam's Club stores in the Washington region. The only superstores are in Fredericksburg and Ashland.

Wal-Mart has only one of its standard-size stores in Montgomery County, in Germantown, and no plans to expand in the county, said Mia Masten, Wal-Mart's community affairs manager for the eastern region.

Still, Wal-Mart opposes the measure. "We think it's anti-competitive and anti-consumer," said Masten. "It not only affects us but other competitors who want to come into Montgomery County and offer consumers one-stop shopping, which is what consumers say they want."

Rival Target, based in Minneapolis, has its own version of supercenters that include a grocery store, but it is expanding them less aggressively than Wal-Mart. There are no SuperTargets in the area.

It's not clear whether the proposed ordinance will win approval from the Montgomery County Council because of uncertainty about whether singling out combination retail stores -- those that sell both food and general merchandise -- would survive a court challenge.

Duncan, in a February memo relaying the legislation to the council, justified restricting such stores but not club membership stores by citing data suggesting superstores generate more traffic.

Yesterday, at a session of the Planning, Housing & Economic Development Subcommittee, however, the Department of Parks and Planning presented data indicating that club membership stores generate more traffic.

The subcommittee requested additional data and will take up the matter again in July. "I don't think we've been provided with enough information to draw a circle around something called a combination retail store and have it pass legal muster," said council President Steven A. Silverman.

The anti-Wal-Mart alliance in Montgomery County reflects a shared interest for the supermarkets and the supermarket union, which recently struck a new four-year labor contract after weeks of preparations for a possible strike.

"We have spoken to coordinate lobbying the bill,'' said Barry F. Scher, Giant vice president of public affairs.

"We are supportive of the concept," said Safeway spokesman Greg TenEyck, although he said his chain has not taken an active role in lobbying for the measure.

Local 400 President C. James Lowthers did not return phone calls seeking comment. But a Local 400 official confirmed that the union is working with Giant to push the bill. "We are communicating about it," the union official said.

Wal-Mart was a backdrop for the contract talks between the chains and the union. During negotiations, supermarket executives cited increasing competition from Wal-Mart and other nonunion retailers as the impetus for proposed benefit cuts.

The preemptive move in Montgomery County did not surprise industry experts.

"A grocery store cannot compete against a supercenter," said Jason Whitmer, analyst at FTN Midwest Research Securities. "The logic is to fight Wal-Mart before they come rather than when they come."

FTN Midwest found that within a year of opening, a Wal-Mart supercenter takes 11 percent of grocery store business within three miles.