Mayor Marion Barry yesterday proposed a six-month delay in implementing the District of Columbia's no-fault automobile insurance law, now scheduled to take effect April 1.

In a letter to the City Council, which must approve any delay, Barry said his administration cannot complete either a review of proposed new insurance rates or regulations to enforce the law in time to meet the April 1 deadline.

Barry also wrote the council that some insurance companies "took the opportunity to request dramatic increases in the rates,"--as much as 32 percent in some cases--and he said he is "concerned that many residents . . . may have difficulty obtaining the funds necessary to purchase the required insurance."

The new law would require District motorists for the first time to purchase autmobile insurance before receiving new registration tags. About 40 percent of the 250,000 registered vehicles do not have insurance now. If Barry's proposal is accepted by the council, motorists could purchase this year's tags without having to purchase insurance.

The council will take up the issue next Tuesday, the same day the Department of Transportation was scheduled to send out tag renewal applications to city motorists. The mailing will be put off at least one day until the council acts, city officials indicated.

The proposed delay would effectively put off enforcement of the law until April 1984 when the majority of the tags would come up for renewal. However, any new tags issued after the six-month delay, which would end Sept. 30 would be subject to the insurance requirement.

Council members who supported no-fault during a long and bitter fight over the issue last year immediately criticized Barry, saying he was using administrative excuses to sabotage the legislation that became law without his signature.

"Once the public learns what's going on, people will be outraged," said Council member Betty Ann Kane (D-At Large). She said the mayor's administration "has created this situation where the enemies of no-fault are now able to use the government to accomplish what they couldn't accomplish directly."

Barry, who has not taken a stand on the no-fault law, could not be reached for comment on Kane's assertions.

The bill emerged after a major fight between insurance companies that favored the measure and trial attorneys who said the law would unfairly limit the right of motorists to sue for "pain and suffering" after accidents.

The no-fault provision would require motorists to use their own insurance to pay their personal injury costs.

Barry's proposal, which as an emergency measure requires nine votes on the 13-member council to pass, is expected to touch off a replay of the acrimonious fight that ensnarled the council for months.

Council member John Ray (D-At Large), a longtime opponent of no-fault, rejected criticisms that Barry's delay was an effort to kill the law.

"I'm going to attempt to get rid of no-fault, but its going to be a direct attack," Ray said. "If there had not been an election last year, the mayor would have vetoed it. If a majority of the council wants no-fault (the supporters) have nothing to worry about," Ray said.

Ray said part of the administrative problem with no-fault is that the new law requires that the insurance rate be approved in advance. Under the old system, automobile insurance rates went into effect and were rarely overturned because insurance was not mandatory, Ray said.