A sweeping measure that would outlaw smoking in taxicabs, many bars and the lobbies or public areas of retail stores and District government buildings received a sympathetic hearing before a D.C. Council committee yesterday.

The proposed ordinance also would require restaurants to establish nonsmoking areas that use barriers and upgraded ventilation to segregate people dining in nonsmoking sections.

Representatives of the business community, the Tobacco Institute and the area restaurant association said the bill as proposed might be discriminatory and would result in significant economic loss to the District.

The bill "would be without equal in its unjustifiable intrusion into private sector affairs in the District," said James M. Christian, a lobbyist for the Tobacco Institute and chairman of the D.C. Democratic State Committee.

Speaking on behalf of the measure, however, were Barry Scher, vice president of Giant Food, and respresentatives from a variety of health-related agencies and associations.

"It's obvious to us that customers do want a smoke-free environment when they shop," Scher said.

The bill, sponsored by council member Hilda H.M. Mason (Statehood-At Large), would exempt restaurants with capacities of up to 25 persons, including customers and employes, and nightclubs and taverns with capacities of up to 75. In nonexempt establishments, the nonsmoking section would comprise half of the seating capacity.

Alexandria officials are considering requiring restaurants to set up nonsmoking sections, following similar moves in Fairfax, Arlington, Prince William, Montgomery and Prince George's counties.

Medical experts at the hearing, most notably D.C. Health Commissioner Reed V. Tuckson, painted a grim picture of the hazards of smoking, noting that 26 percent of District residents smoke and that D.C. residents have the highest rate of cancer in the United States.

Barry administration officials stopped short of embracing Mason's idea. Eileen Hemphill, the acting chief of the city's Office of Consumer Education and Information, said that the mayor would prefer that an economic impact study be performed before the council acts on the measure.

While calling the council proposal "well-founded," she said that the Barry administration is "concerned with the effect it will have on the business community."

"I view human life as being more important than any money that restaurants would lose," Mason responded.

Tom Rouland of the Restaurant Association of Metropolitan Washington opposed Mason's bill but said his association favors legislation requiring restaurants to establish nonsmoking sections. The size of such areas, he added, should be determined by the individual restaurateur, not by the government.

In 1979, the council enacted a law banning smoking in elevators, city buildings, schools and health care facilities.

In 1985, council member Nadine P. Winter (D-Ward 6), who is chairman of the Public Works Committee that is considering the measure, voted against a more stringent measure, which failed. Yesterday, however, she appeared to relent, publicly scolding the mayor's representatives for failing to give the bill unequivocal support.