A government-sponsored campaign to warn the public about the potentially fatal tendency of some Ford Motor Co. vehicles to slip from park to reverse has failed, according to a preliminary study released yesterday by the General Accounting Office.

The study, presented to a House subcommittee, said 226 fatalities attributable to the suspected defect have been reported since December 1980, when the National Highway Traffic Safety Administration began its "public awareness" campaign on park-to-reverse problems.

The campaign was aimed at owners of Ford cars and trucks manufactured for the 1970 through 1979-model years. Many of those vehicles, about 20 million of which remain in operation, supposedly are equipped with automatic transmissions that can slip from park to reverse without warning.

As part of the "public awareness" effort, Ford sent labels to owners of the affected vehicles warning them that, under certain conditions, their transmission levers might not engage fully in "park," even though the shift indicator might read "park." The labels were to be affixed to a dashboard or some other prominent place in the car or truck.

The campaign was part of a settlement of an "initial finding of defect" the NHTSA made in the Ford case. The "initial finding" -- a preliminary determination always open to subsequent reversal under the NHTSA's rules -- was made after a three-year agency investigation that began in 1977.

Before the 1980 settlement, there were 110 reported Ford-related park-to-reverse deaths involving 1970 to 1979 vehicles.

Of the park-to-reverse deaths reported after the settlement, 88 actually had occurred before the agreement and 138 had occurred after 1980, the GAO report said.

But critics of the NHTSA's handling of the matter said that the number of post-1980 fatalities probably is higher but unaccounted for because the NHTSA scaled down its park-to-reverse investigations after 1980.

The GAO report backed the charge that the NHTSA relaxed its investigation after the agreement.

Democratic members of the House subcommittee on telecommunications, consumer protection and finance yesterday used the GAO report to renew attacks on the NHTSA and its current administrator, Diane K. Steed. One subcommittee member demanded Steed's resignation.

Steed previously told the subcommittee that reported Ford park-to-reverse deaths had decreased since December 1980, a position she maintained under withering criticism yesterday.

Steed also defended her agency's July 12 decision not to reopen the case. The Ford vehicles in question are no more prone to park-to-reverse malfunctions than other makes, foreign and domestic, now running on American roads, she said. "Our conclusion is that we simply cannot find a mechanical defect in these cars. Instead, we've found that all cars have this type of problem," Steed said.

Subcommittee Chairman Timothy E. Wirth (D-Colo.) accused Steed of trying to cover up the matter.

"I can only conclude that Ms. Steed has become the Rita Lavelle of safety," Wirth said, referring to the former assistant administrator of the Environmental Protection Agency who was convicted of perjuring herself before Congress.