A lawsuit filed yesterday against the National Highway Traffic Safety Administration alleges that the government illegally cooperates with automakers in research leading to federal auto safety laws.

Public Citizen, the parent of a chain of lobbies founded by consumer activist Ralph Nader, drafted the petition that was filed in U.S. District court here.

Since October 1982, NHTSA "has been conducting a secret cooperative research program with the Motor Vehicle Manufacturers Association, a trade association which consists of representatives of all domestic automobile manufacturers," the suit said in part.

As a result, the suit alleges, NHTSA "has received recommendations directly from the MVMA regarding NHTSA's general research activities and priorities"--including research on tests designed to yield new safety standards for doors and other barriers that could protect car passengers in lateral collisions.

The charges have been made numerous times before by Public Citizen President Joan Claybrook, former administrator of the NHTSA. But "they wouldn't stop holding the secret meetings," Claybrook said yesterday, explaining why she is taking her case to court.

The media received Claybrook's petition before the defendants, which left most of them unable to respond yesterday.

However, NHTSA repeatedly has denied holding secret meetings, calling its meetings with automakers and their representatives "coordinated research."

"The goal of coordinated research is to get as much information as we can from the private sector, and to trade as much of our own information as possible without compromising our safety mission," said NHTSA spokesman Richard Burdette.

NHTSA said in December that it would study ways to allow more public participation in coordinated research projects. But Burdette said yesterday that the agency has not yet found a way to open up the meetings without endangering corporate product development plans, which normally are regarded as proprietary information.