Consumer activist Ralph Nader accused President Reagan of being "squarely in the glove compartment of General Motors" and said at a news conference today that an escape clause in a federal transportation order will substitute "toothless" seat-belt laws for air bags in new cars.

In another skirmish in the escalating seat-belt battle in state legislatures, Nader said automobile manufacturers' support for mandatory seat-belt laws is "a manipulative and callous strategy to avoid the expense of installing air bags."

Last year, Transportation Secretary Elizabeth Hanford Dole issued an order requiring new cars to be equipped with air bags or automatic selt belts by 1989. The order would be rescinded automatically by the passage of mandatory seat-belt laws by states whose combined populations represent two-thirds of the nation's populace.

New York, New Jersey and Illinois have enacted laws requiring motorists to wear seat belts, but Dole has not ruled whether those laws meet the order's standards. The governors of Michigan and Missouri have promised to sign seat-belt laws passed by their legislatures.

A seat-belt law was killed in committee today in Arkansas, and five other states, including Maryland and Virginia, have rejected similar laws. Measures are pending in seven states.

Four separate mandatory selt-belt laws have been introduced in the California legislature. One, by Assembly Speaker Willie L. Brown Jr. (D-San Francisco), was written to exclude California from counting toward the two-thirds-population requirement and would require cars sold in California after Sept. 1, 1989, to have air bags or automatic seat belts even if the Dole order is rescinded.

Brown's bill has been endorsed by Nader, local consumer groups and a number of physicians. Brown's bill also has the support of much of the insurance industry, which says air bags reduce injuries to crash victims and thus mean fewer and smaller settlements.

Automobile industry groups support a rival bill likely to meet the order's standard.

Nader was joined at the news conference by two car-crash victims. Annette Paluska, a former Miami Dolphins cheerleader, said she tried to have air bags installed in her Chevrolet Vega before she suffered brain damage in a 1980 crash. She said she was told that her car would not accommodate the bags.

Paluska said she was wearing her seat belt when the accident occurred, "but it couldn't save me . . . . It was ripped from the floor in the crash."

She added, "It's hard for me to believe that Elizabeth Dole is driving around in a car with an air bag, while she's preventing other Americans" from enjoying the safety measure. A spokesman for Dole, Robert S. Marx, said the secretary's official car, a Lincoln Continental, had been retrofitted with air bags at Dole's request.