A controversial study by the Department of Transportation showing widespread consumer problems with Firestone 500 steel-belted radial tires was apparently accidentally "leaked" to a consumer group, according to a spokesman for the Carter for Auto Safety, the Nader group that eventually released the study.

The survey, which was conducted by DOT's National Highway Traffic Safety Administration, is the subject of a bitter court battle in which Firestone Tire & Rubber Co. is seeking to identify the source of the report's release. A federal judge had forbidden its release earlier.

The report shows that almost half of all Firestone 500 tire owners who responded to a survey had problems with their tires - including tread separation and blowouts. The percentage was significantly lower for the owners of five other major brands of steel-belted radials.

Last month, after Firestone said it had received a sample of a survey card, the firm went into U.S. District Court in Cleveland to halt release of the study, claiming that it was "inherently defective and its results would be biased and unfair to Firestone."

Judge John Manos issued a temporary restraining order preventing DOT from releasing the results of the study until an investigation of its contents could be made.

Meanwhile, The Center for Auto Safety filed a Freedom of Information Act request with DOT, asking for a copy of the study and several other documents. DOT officials confirmed yesterday that an FOI request from the center was filed.

According to a letter froM CAS Executive Director Clarence Ditlow to Firestone Chairman Richard A. Riley released yesterday, "The request was largely granted but the survey was denied to us on the ground that a law enforcement proceeding was still in progress."

But when the package with the other documents arrived under separate cover, "we discovered the memorandum containing the survey results in the middle of the pile. We have no idea how it got there," said Ditlow.

Ditlow subsequently held a press conference and released the report. He charged that the tires were responsible for at least five deaths.

Last week, Ditlow and several others, including 12 DOT officials and three journalists, were subpoenaed to give depositions to Firestone lawyers about the report's release. Ditlow is scheduled to give his deposition this morning.