The Justice Department, without public announcement, has refused to renew key provisions of a consent decree with the automobile industry 10 weeks after President Reagan had urged a similar action asking the department to take a "fresh look" at the constraints of the decree.

The decision, a reversal of Carter administration policy, tossed out provisions of the 1969 decree between the government and the four major domestic auto manufacturers and the Motor Vehicle Manufacturers Association. The provisions barred the auto companies from exchanging research information on emissions control and from filing joint statements with government agencies handling emissions and safety standards.

These provisions, which were designed in large part to encourage the auto companies to compete on new environmental and safety technology, were valid for 10 years, or until 1979, just after the Carter administration recommended their renewal.

At the time, the Environmental Protection Agency, the National Highway Traffic Safety Administration, and the California Air Resources Board told the Justice Department's Antitrust Division that in may cases advances in emission-control technology were "directly attributable" to the prohibitions of the decree.

In a May 20 memo to Attorney General William French Smith, Reagan said that EPA and the Department of Transportation have adopted new policies on the question of joint statements to government agencies as a way to lift regulatory burdens from the industry.

"In addition, the manufacturers party to the decree have asked you to consider whether it would be appropriate to vacate the consent decree," Reagan wrote. "Although this may not result in relaxation of the constraints imposed upon the industry, the time has come for a fresh look at the parameters of those constraints.

"In light of the foregoing, I ask you to expedite your consideration of this request, once the pending appeal concerning the decree has been concluded," Reagan wrote.

In fact, Assistant Attorney General for Antitrust William Baxter told EPA Administrator Anne Gorsuch in a letter that the Justice Department had opened a review of decree at "the President's request."

The Carter Justice Department had asked for the renewal in 1979, but that effort was denied by a U.S. District Court Judge. The government appealed that decision, and the case was remanded on April 23, 1981, back to the court for an evidentiary hearing. Justice Department attorneys contended yesterday that the decision not to continue to pursue the renewal was based on their belief that they had no new evidence to present to the court and would lose the request again.

But a citizen's group, the Center for Auto Safety, which raised the issue in a letter to Baxter yesterday, charged that the decision was a political manuever designed to aid the industry in the fight over emission standards.

"Since the Reagan administration is engaged in a wholesale attack on the automobile emission standards, the timing of this secret deal with the auto companies has all the earmarks of a political manuever to enable the auto companies to present a united front in their efforts to weaken the Clean Air Act," said Clarence Ditlow III, director of Center for Auto Safety, in the letter to Baxter.