President Carter's auto safety director, Joan Claybrook, took sharp issue with a Ronald Reagan transportation advisory group yesterday, disputing its week-old report that the government can no longer make cars much safer without adding unreasonably to their cost.

Claybrook disclosed that she has sent the chief executives of all the world's automakers a list of two dozen additional safety features she said could save thousands of lives "at minimal or negligible cost."

Her list includes such proposed new features as brake wear and low tire pressure indicators, bigger rear brake lights, more interior padding and plastic linings on windshields to protect against broken glass on impact.

A Reagan task force concluded last week that Claybrook's National Highway Transportation Safety Administration "has effectively exhausted its ability to increase automobile safety at reasonable social cost."

"I challenge them to show any basis for that," Claybrook said when she was asked about the Reagan report at a NHTSA news conference on tire grading standards. "I don't think there's any basis for that statement."

Government safety standards have been responsible for only 2 percent of the increase in the cost of cars in the last seven years, Claybrook said. And only three of the safety features required by the government cost more than $10 each.

"That's a very, very meager cost compared to the improvement in safety," she said.

"Cars can be made measurably safer" at minimal cost, Claybrook said, if manufacturers would design safety improvements into their cars while they are still on the drawing boards instead of waiting for the government to tell them what to do.

All the car makers are designing new, smaller, more efficient cars, Claybrook said. In a letter sent to the chief executive of every company selling cars in the United States, Claybrook said, "There are a number of priority safety performance features which should and readily can be incorporated in your vehicles as you improve them and redesign them."

NHTSA officials said the agency has received no response from the auto companies to the 11-page letter. The U.S. car makers are closed down for their Christmas vacation this week, and company officials could not be reached for comment yesterday.

Claybrook told the companies that there are "readily available remedies within the present state of the art" that could reduce the nation's highway death toll. Every day 140 people are killed in accidents on American highways.

Federal safety standards have reduced the deaths by 10,000 a year, Claybrook said. To cut the body count further, she suggested that designers improve occupant restraints to keep passengers from smashing into the dash or windshield and build cars that will better absorb the impact of crashes.

She said that cars could have better braking, handling and visibility so drivers can avoid accidents, and that bumpers and hood ornaments should be redesigned to protect pedestrains from injury.

At the top of Claybrook's list of specific suggestions are the air bag and the controversial "passive restraint" standards that NHTSA and the auto companies have been fighting over for years. "With automatic crash protection, an occupant's risk of death and serious injury can be reduced by about 50 percent," saving 250,000 lives in the next 20 years, Claybrook said. a

NHTSA now plans to make air bags or other passive restraints mandatory by 1983. The Reagan transition report said the air bag rule "should be considered carefully in order to avoid unjustifiable expenses by manufacturers and, in turn, consumers."

Adding passive restraints -- either air bags or automatic seatbelts -- would cost an estimated $115 a car, making it the most costly federal safety standard so far. The only other safety features that added more than $10 to the wholesale cost of cars, Claybrook said, are crash-resistant bumpers, $54; three-point seatbelts and retractors, $37, and side impact beams, $24.

NHTSA is working on new rules for improved protection in side impact crashes, which kill 10,000 people a year, and new pedestrain protection measures to reduce the 8,000 annual deaths.

Claybrook's shopping list of additional safety features includes:

Seatbelts that are more convenient and comfortable, so more people will use them.

Interior padding, especially on the lower dashboard, doors and seatbacks to reduce injuries to passengers, particularly children, who are tossed around the inside of a car.

Windshields lined on the inside with a layer of plastic to keep sharp pieces of glass from cutting the faces of passengers in accidents.

Safer fuel tanks to prevent fires, and fire-resistant barriers between the tank and the passenger compartment.

Bake wear and low tire pressure indicators to warn of potential failure.

Silicone brake fluids that last longer and prevent brake system corrosion.

Bigger brake lights, mounted high in the center of the car, which studies show reduce rear-end crashes.

Soft bumpers, rounded fenders and flush hood ornaments to minimize injuries to pedestrains struck by cars.