The vote by the ozone assessment group was significant because the vast majority of states endorsed aggressive measures to control smog.

Connecticut will not accept strict new standards on automobile emissions as part of a regional effort to control smog, Gov. Lowell P. Weicker Jr. said.

A vote here by representatives of the 12 governors and of the Mayor of the District of Columbia was the latest of several efforts by the group to be more vigorous in controlling smog than Federal standards require.

Federal standards for gasoline vehicles set a limit on hydrocarbon emissions as a way to control smog, but proponents of natural-gas vehicles complain that natural gas itself, while a hydrocarbon, is not an ingredient of smog.

The state authorities also said the rule would make it exceedingly difficult to enforce portions of the Clean Air Act designed to control urban smog, and they predicted that many states would ignore the Administration's regulation and enact tougher standards.

Experts predict that solving the problem will cost billions of dollars and will rival the efforts to control smog.

Nitrous oxide, or N2 O, is not regulated because the Clean Air Act was written in 1970 to control smog, not global warming.

AFTER two decades of progress, the campaign to control smog from cars and trucks is now losing ground because of an enormous increase in the number of vehicles on the road.

Dan Weiss, the political director of the Sierra Club, called the power companies' move "an unbelievable assault on efforts to control smog and acid rain."

Experts differ on how much the ingredient has done to control carbon monoxide and smog, but they agree that it has cut toxic components from gasoline in the air by about 30 percent.