A small, quiet, and clean cadre of hybrid taxicabs will soon dot city streets, but some members of the City Council disagree with the Taxi and Limousine Commission about how and when the cabs should appear.

The council’s Transportation Committee has a hearing scheduled for today on a bill that would allow the commission to introduce the gas-electric hybrids into its fleet of yellow cabs faster. Current regulations require taxis to have more passenger room in the backseat than is standard in hybrids.

“We have spoken about the need to do this with the TLC several times,” the chairman of the Transportation Committee, Council Member John Liu, said. “There doesn’t seem to be any movement, so I have called for a hearing to push this legislation forward.” Mr. Liu, a Democrat of Flushing, is a co-sponsor of the bill. Last year the council passed a law requiring the commission to designate a certain percentage of the medallions it sells as for clean vehicles. Cab owners purchased 19 medallions for clean vehicles, but the commission declined to approve any hybrids because of the rules on passenger space.

Matthew Daus, the TLC commissioner, has said he opposes lifting the space requirements because it would take control away from the commission, which is planning a pilot program of its own on a more gradual timetable.

“We share the goal of cleaner air with the council, but we respectfully disagree on how to get there right now,” Mr. Daus said yesterday in a phone interview. “Even though the council members’ objectives are pure and good … I want to go prudently. I don’t want to see us repeat mistakes of the past.”

A decade ago, the commission introduced a limited number of taxi engines that burned compressed natural gas. Mr. Daus characterized the program as a flop. “It was too much, too soon. There was such a push to get a rule passed, and the program failed,” he said. “There were too high expectations, and people lost money.”

An energy professor at the Fletcher School at Tufts University, Bruce Everett, said Mr. Daus’s prudent approach makes sense. He cited a federal policy that was implemented several years ago requiring certain government-owned automobiles to have clean-fuel engines. The policy, he said, was not economical.

“As a matter of public policy, I don’t think the government ought too be too intrusive, and impose costs on the public for symbolic reasons,” Mr. Everett, who worked for Exxon Mobil for 22 years, said. In addition, the publisher of Taxi Talk magazine, Michael Higgins, questioned the “circus-act contortionism” that would be required for a passenger to squeeze into the backseat of some of the smaller hybrid models. Bigger models are expected to be available soon.

Still, Mr. Daus said introducing hybrids is “a top priority” for the commission. On Monday he is scheduled to present a plan to the commission to test in the “near future” a small number of hybrid vehicles and gauge, among other variables, vehicle performance and riders’ reactions. The commission’s goal, he said, is to sell 81 alternative-fuel medallions before July 2006.

Council Member David Yassky, a Democrat of Brooklyn, said, however, that he would like the council to vote within the next year to require that all new city cabs have clean-fuel engines.

“They cannot come to us now and say we want a pilot program. We asked for that two years ago,” he said. “… I don’t think we need to wait. Hybrid cars at this point are well enough established to know they can function as taxis.”

Both sides acknowledge hybrids will save money and pollute less. When asked whether the council was overstepping its authority, Mr. Liu defended the council’s involvement.

“Within a few years, all cars will be clean,” he said. “Our job is to be a catalyst for that change.”