General Motors, citing possible injury to small children from passive restraints, yesterday announced it was delaying the planned introduction of airbags in its 1981-model cars.

Federal safety officials immediately challenged the GM decision, claiming the company was using inadequate testing results as an excuse to delay the airbags.

The announcement came as the Supreme Court refused to consider a challenge to a Department of Transportation requirement that all automakers begin phasing in passive safety restraints in their 1982-model cars. The law does not mandate the use of airbags. Companies can use other forms of passive restraints such as automatic seat belts.

Joan Claybrook, administrator of the National Highway Traffic Safety Administration, told a news conference yesterday that she was appointing a special task force to study any "remaining issues" involving airbag performance.

Consumer advocate Ralph Nader yesterday claimed the delay was part of a "well-orchestrated, behind-the-scenes attempt by GM to destroy adoption of the greatest life-saving technology on the highways."

GM had planned at first to offer airbags as an option on 1981-model cars. But earlier this year, the company said it would delay that introduction until the middle of the 1981-model year.

Last week, however, in a letter to Claybrook, Betsy Ancker-Johnson, GM'S vice president for environmental activities, wrote that the company has decided to further delay the airbags because of new problems.

"Through extensive development testing," she wrote, "we became concerned about the potential for risk of injury to unrestrained small children."

Ancker-Johnson said GM studies "suggested that due to the effect of pre-impact braking on unrestrained children, or because they might not be seated properly at the time (the airbag inflates), they might be exposed to inflation forces capable of producting significant injury."

"We are continuing our engineering development efforts with the goal of introducing such an option on full-size cars in 1982," Ancker-Johnson said in her letter, adding that GM may still have a driver-side airbag option by 1981-model cars.

"GM has made important improvements in the new generation of its Air Cushion Restraint Systems," Claybrook said at her press conference. "We are excited with the work they have done. Thus it is especially disappointing that on the basis of such conjectural conclusion, GM now has decided to withhold from the market in 1981 a safety system that has been convincingly proven to save lives and significantly reduce injuries in auto crashes."

Claybrook said that even if the GM claim was valid, it was a very narrow problem based on "fragmentary and specualtive" data. "In the real world," she said, "airbag-equipped cars built by GM have been performing very well."