A controversial antipollution plan that would require yearly exhaust tests for all cars registered in the Washington area and would ban free parking here for government employes was approved yesterday by key regional officials.

The adoption of the plan by the board of directors of the Metropolitan Washington Council of Governments, which includes influential officials from the District of Columbia and suburban Maryland and Virginia governments, set the stage for renewed political battles over the area's long-standing efforts to reduce air pollution.

The COG recommendations, which have been under study since July, are intended to help the District, Maryland and Virginia comply with federal antipollution requirements incorporated in last year's congressional amendments to the Clean Air Act. The hotly debated proposals are aimed to curbing the Washington area's most severe and obdurate air pollution problems - those caused mainly by automobile exhausts.

A similarly controversial 1973 plan - imposed on the Washington area by the U.S. Environmental Protection Agency - was largely shelved after becoming embroiled in a bitter dispute that entailed congressional objections and court challenges. Some federal and Washington area officials say, however, that the new plan appears more likely to survive, partly because of changes in federal antipollution laws.

The COG plan would require motorists in the Washington area to have their cars inspected annually to make certain that their exhaust pipes did not spew out excessive pollution. Such auto-exhaust tests are expected to become mandatory throughout much of the United States within the next few years because of federal antipollution laws.

Auto owners whose cars flunked the pollution tests would be complled to pay for repairs. A 1976 consultants' report on Washington's pollution problems estimated that repairs and possible inspection fees would cost typical car owners here $40 a year. COG's newly approved report described auto-exhaust tests as the measure "with the greatest potential for improving air quality" in the area.

The Maryland and Virginia legislatures have repeatedly refused in the past to set up such programs, but some officials say that legislative sentiment may be changing, partly because of a new threat of federal sanctions. Failure to comply with the Clean Air Act amendments may result in a cutoff of federal highway, water and sewer funds.

Maryland State Sen. Harry J. McGuirk (D-Baltimore), whose Economic Affairs Committee recently held a hearing on auto-exhaust testing, said yesterday he believes there is a "real good possibility" that the Maryland legislature will move to establish an exhasut inspection system next year because of the possible federal sanctions, Virginia officials also have expressed similar views recently.

Efforts by Washington area officials to persuade the federal government to stop providing free and low-cost parking spaces for federal employes also have encountered strong resistance from key federal agencies. Many local officials argue that increased parking fees would deter some employes from driving to work and would, therefore, lessen pollution stemming from auto-exhaust fumes.

Several COG board members sharply criticized the federal government yesterday for its failure thus far to eliminate free and low-cost employe parking. A spokesman for the Office of Management and Budget, which is currently reexamining the issue, said that OMB's recommendations will be announced soon.

A recent federal study found that federal government agencies provide about 28,000 free or low-priced parking spaces for their employes and that Congress has about 9,000 additional free parking spaces.

The COG plan approved yesterday included a wide range of other antipollution proposals. Among them were further prohibitions against onstreet parking for commuters, encouragement of increased car-pooling, completion of the planning Metro subway system, and controversial measures to reduce gasoline fumes at service stations.

The recommendations were sent to the District, Maryland and Virginia governments, which are required to submit official antipollution plans to EPA by Jan. 1. As expected, the COG report concluded that the Washington area cannot meet federal clean-air standards by 1982, EPA's initial target date. It proposed an extension until 1987, the final EPA deadline.

The COG proposals are aimed at curbing two major pollutants - smog and carbon monoxide, both of which are largely byproducts of auto exhausts. Smog, also known as photochemical oxidants, consiss chiefly of ozone.