Metro officials and local fire chiefs, responding to concerns raised by the subway fire in London that killed more than two dozen people, said yesterday that Washington's transit system is one of the most fire-safe and that further improvements are under way.

Metro is "certainly one of the best systems in the United States" in terms of fire safety, said Walter Wise, chief of the Bethesda Fire Department.

Echoing that comment, District Fire Battalion Chief Ambrose Murphy, the department's liaison with Metro, said he disagreed "wholeheartedly" with suggestions that Washington could experience a fire similar to the one Wednesday night in London's King's Cross station.

The fire, which broke out at the end of evening rush hour, apparently started on a decades-old wooden escalator leading up to the station's main ticket hall. The cause of the fire was under investigation.

"You can't compare the two" subway systems, Murphy said. "There are no combustibles" on the Metro system, which is constructed primarily of concrete, steel, bronze and tile, he said.

However, Tom Tippett, president of the D.C. Firefighters Association, told United Press International that a subway fire here is inevitable and that Metro is ill-prepared.

"It's not a question of if, it's just a matter of when," said Tippett, noting that Metro has yet to make improvements in its ventilation system that were recommended after a fatal Metro accident in January 1982. Metro has never had a fatal fire in its 11 years of operation.

Murphy said that at the regular bimonthly meeting of local fire chiefs and representatives yesterday, he asked if any of them had criticism or concern about Metro's fire preparedness. None did, he said.

Thirty-three miles of Metro's 69.6-mile system are underground. Emergency exits, with stairs leading to the ground level, are located throughout the system, William W. Curtiss, Metro's fire protection coordinator, told reporters during an underground tour yesterday.

Metro tunnels have smoke detectors, underground water pipes, fans and vent shafts, Curtiss said. At stations with only one exit, such as Eastern Market and Capitol South, sprinklers have been installed to douse any smoldering waste paper or grease that a dropped cigarette might ignite, Curtiss added.

London's subway does not have sprinklers or smoke detectors, transit officials there said yesterday.

Metro officials said Washington's subway system was built to be as fireproof as possible, and that the agency learned several lessons from the 1982 derailment at the Smithsonian station in which three persons died and 25 were injured.

Metro has implemented almost all of the more than 200 safety recommendations it received from federal and transit industry safety experts after the derailment, including one from London Transport, said Carlton R. Sickles, chairman of the Metro board's safety committee.

The improvements include increased training and drills with local fire and rescue personnel, better signs to help passengers find emergency exits, and a special computer system to speed emergency response. Metro also purchased breathing equipment for firefighters.

Critics note that Metro has not yet made improvements such as installing tunnel evacuation carts, changing its ventilation system and removing all PCB coolants, which would emit toxic gas in a fire.

Metro officials say that the evacuation carts are under construction, with the first 95 expected by summer; that the PCBs are being removed and should be eliminated by 1990, and that about $40 million will be spent to improve the ventilation.