A D.C. City Council committee, after five hours of often heated debate, voted yesterday to back Mayor Marion Barry's call for a six-month delay in implementing the city's compulsory no-fault auto insurance law.

The 3-to-1 vote--a warm-up for an expected full council fight on Tuesday over the mayor's proposal--came after city officials said they probably could implement the law by the original April 1 deadline, but not in time to give motorists adequate time to shop for insurance.

"I've heard every excuse possible," snapped an obviously angry Hilda Mason (Statehood--At Large), who backs no-fault and was the only committee member to oppose the delay.

The new law, which for the first time would require motorists to buy auto insurance, mandates that auto insurance rates be approved before they go into effect. Previously, companies applying for rate increases were allowed to put those rates into effect while waiting for approval from the superintendent of insurance, with the proviso that refunds would be made if the rates were disallowed.

Yesterday, Corporation Counsel Judith W. Rogers and Department of Transporation Director Thomas M. Downs said that by the time the new rates submitted by companies under the no-fault law are approved, too little time may be left for motorists to purchase insurance before the April 1 deadline for annual tag renewal.

The law requires motorists to certify they have insurance before they can receive tags. Officials estimate that about 100,000, or 40 percent of the city's 250,000 registered vehicles currently are uninsured.

Council member Betty Ann Kane (D-At Large), objecting to the delay, told the Committee on Consumer and Regulatory Affairs that provisional rates could go into effect while the superintendent of insurance studies the long-term rates.

Brian Ledderer, head of the Office of the People's Counsel, suggested in written testimony that temporary, 90-day rates could go into effect while the long-term rates are being reviewed and that any refunds to consumers include 12 percent interest paid by the insurance companies.

Kane, who is not a member of the committee, and some other council members have said the delay is an effort by the mayor to kill the no-fault bill, which passed last year after a lengthy political fight. Barry, who allowed the bill to pass without his signature, has denied those allegations.

Voting for the delay were council members John Ray (D-At Large), chairman of the committee, Charlene Drew Jarvis (D-Ward 4) and Frank Smith (D-Ward 1).

Approval of the delay would require backing by at least nine members of the 13-member council.