A recent European Community decision to tighten car exhaust standards, which ended a bitter year-long debate over the adoption of U.S.-style regulations, has left both environmentalists and automobile manufacturers unhappy.

Environmental groups said the community decision to reject the strict application of the U.S. regulations, in favor of standards that officials believe will have an equivalent effect on air quality, was designed to meet the needs of the ailing European car industry.

"This is just another example of Europe remaining backward in comparison with the United States and Japan," said Ernst Klatte, the secretary-general of the European Environmental Bureau. A study released by his group found that the new regulations will lead to "significantly more pollution, both short term and long term."

But automobile manufacturers said the community acted hastily under pressure from certain EC states, in particular West Germany, to do something about acid rain and the highly publicized phenomenon of dying forests and lakes in Europe. The Liaison Committee of the Motor Industry, a lobbying group that represents European car makers as well as Ford Motor Co. and General Motors Corp., said the EC's "drastic decision" ignored the lack of scientific evidence linking car exhausts and forest damage, and disregarded progress already made in reducing emissions.

The state-owned British Leyland company, the country's top producer, said that meeting the new standards could add $1,400 to the cost of a family car. European manufacturers said the additional cost could cut their annual sales of 8 million cars by 10 percent, while opening the market further to cheaper, low-polluting Japanese models.

Along with the United States, the community began attempts to control car pollution in the early 1970s. While the EC standards, unlike the American regulations, are voluntary on a communitywide basis, the car industry generally has adjusted engines to meet the standards to avoid exclusion from countries that have written them into their national legislation, EC officials said.

The officials are hesitant to make comparisons of the relative strictness of emission standards as they have developed in the United States and the community, since driving conditions and average car engine size are significantly different. One important distinction between their pollution control efforts is that catalytic converters have not been developed for the small engines in most European cars. Manufacturers said the converters would sweep away most of the advantages of their cars by reducing fuel economy and performance and inflating the price tag.

Current U.S. regulations, however, have been used by European environmentalists and some member states as a measure to judge the adequacy of EC controls.

As the European Commission, the EC's executive body, was preparing new standards last year, West Germany declared that it would require all new cars to meet the U.S. regulations by 1989. The Bonn government, under strong electoral pressure from a growing environmentalist movement, alarmed EC car makers by adding that it would "go it alone" with the new requirements if there was no agreement on tighter controls.

West Germany found general support from the Netherlands and Denmark, while encountering resistance from Italy, France and Britain. The car makers of the latter three countries, which specialize in the production of small- and medium-sized automobiles, said the West German deadline only could be met by equipping the cars with expensive, fuel-inefficient, three-way catalytic converters, like those already in use in the United States.

Manufacturers also wanted more scope for the development of the low-polluting engine known as "lean-burn," which they said was more efficient and potentially less expensive than the catalytic converter.

In the end, West Germany made substantial concessions under pressure from its EC partners during the two key series of negotiations between environment ministers in March and June.

Of the 10 member states, only Denmark, which wants tougher standards, refused to approve the new guidelines, which were adopted June 28.

Klatte criticized the deliberations of the environment ministers, which he said were "dominated by the interests of the Italian, French and British car industries."

Owing to the drawn-out timetable for implementing the standards, and the 10-year period it takes to replace the 100 million cars in the community, the new standards will not be completely in force until after the year 2000, he said. A study prepared by Michael Walsh, a former official of the U.S. Environmental Protection Agency, found that by the time all the EC cars meet the new standards, nitrogen oxide and hydrocarbon emissions will be almost three times higher than U.S. equivalent levels, and carbon monoxide emissions almost 2.5 times higher.

Arnold Price, a staff member of the commission directorate for the environment, defended the new EC standards as a reasonable compromise between the interests of the environmental and car manufacturer lobbies.

If overly strict standards had been adopted, Price said, "you would have had cars nobody could afford to buy." But he believes the new guidelines could result in the faster development of more efficient and cleaner engines.