The Department of Energy, backing off from original plans to go directly to Congress with a request for deregulation of gasoline at the pump, yesterday opened up that proposal to public comment. The action effectively postpones any possibility of deregulation until August - and possibly and as late as next year.

There weeks ago DOE officals were on the verage of going to congress with the deregulation proposal, which would have required a veto by the Senate or House within 15 working days to keep it from going into effect.

But consumer groups and the Environmental Protection Agency attacked the plan because of fears that, under deregulation, the difference in price between unleaded and leaded gas would widen, and there would be considerable "fuel switching" - where motorists who are supposed to buy unleaded gas instead buy leaded because it is much cheaper.

But the DOE contended that since gas was now in plentiful supply and generally selling below the current price ceilings imposed after the 1973 oil embargo, regulation was no longer needed and would not result in increased prices.

But Clarence Ditlow of the Center for Auto Safety, a Ralph Nader consumer group, and officials of the EPA said that unleaded gas is selling near the ceiling, and only leaded gasoline was selling at much lower prices - up to eight or ten cents below unleaded gasoline. Ditlow had threatened to sue the agency if it failed to call for public comment on the need for an environmental study.

Newer autos must take only unleaded gas to meet the EPA's pollution standards. But because of the huge price differential, the consumer groups contend, many motorists are illegally using the cheaper and dirtier gasoline in their cars.

And, Ditlow says, the DOE must do an environmental impact statement to determine what the effects of deregulation would be on the price differential. He claims the differential will widen, and many motorists will be contributing to worsening pollution problems.

EPA officials also claim that more study is needed before DOE deregulates motor gasoline. A new study evaluating the motivation of drivers to switch from leaded to unleaded has just been authorized by the EPA and is expected to be completed within a month.

Sources at DOE confirmed that the agency essentially backed off on its previous stand, instead choosing to take the public route. In a Federal Register notice today, the agency is inviting public comment until July 18, and will hold hearings on July 12 on its decision to forego an environmental impact statement because, the DOE contends, it is not needed.

Congressional sources told The Washington Post yesterday that Rep. John Moss will convene hearings of his Oversight and Investigations subcommittee within two weeks to study the DOE decision to deregulate gasoline at the pump.

Ditlow said yesterday, "Now that the initial attempt to railroad gasoline decontrol through has been averted, we are confident that the public hearing will expose both the enormous consumer ripoff associated with exhorbitant leadfree gasoline prices and the large environmental impact as consumers switch to leaded gasoline to avoid the ripoff."

EPA officials said they, too, were pleased with the new DOE plan to solicit public comment.

"They (DOE) even asked Marvin During (EPA's Assistant Administrator for Enforcement) to participate on their panel at the hearings," said one EPA source who requested anonymity. "So at least now they are trying to get us in the same boat with them."

A DOE spokesman said yesterday that if the DOE decision to go ahead with a deregulation proposal without an environmental impact statement is upheld by public comment, it is likely the proposal will reach congress by about August 1, 1978.

"But," he added, "if it is decided that we have to do a lengthy impact report, I don't think we can propose any kind of deregulation until next year at the earliest."