Consumer activist Ralph Nader yesterday accused the Ford Motor Co. of deliberately delaying the recall of 1.5 million Pintos to correct potentially dangerous gasoline tanks.

Nader, in a letter to company chairman Henry Ford, accused the auto maker of trying to get the National Highway Traffic Safety Administration "to accept a cheap technical fix for the hazardous fuel tank design that will not meet minimum safety precautions."

Nader also accused the company of delaying the recall in an effort to reduce the number of cars involved.

Joan Claybrook, NHTSA administrator and a former consumer lobbyist for Nader, disputed Nader's charge. She said the company has been "relatively responsive" to the tank problem.

"I think they've been pretty responsive." Claybrook said, noting that the company has conducted quite a number of crash tests during the last month and a half in an effort to develop a leak-proof fuel tank.

After learning of Claybrook's defense of the company, Nader accused both Ford and NHTSA of engaging in "mutual foot-dragging."

"On the Ford side," he said, "they should have been ready to go immediately (after NHTSA concluded that the Pinto had a safety defect)." For its part, he said, NHTSA was too slow in initially determining that the Pinto had a safety defect.

A spokesman for Ford, without commenting on the Nader letter, said that official recall letters would be sent to Pinto owners shortly.

Ford announced the recall of the 1.5 million Ford Pintos and Mercury Bobcats June 9, shortly before NHTSA had scheduled hearings that could have led to a government-ordered recall to correct possible fuel tank problems. The NHTSA hearings were then cancelled.

At the time announced he recall, Ford said it would take up to three months to send out the recall letters.

Nader, in his letter to Ford, said the company was considering modifications to the Pinto fuel tank as though "the process of engineering adaptation for Pinto fuel tanks were in its early stages."

But, Nader said, "the fact is that Ford Motor Co. has known for years how to fix its Pinto fuel tanks. What the company is doing is simply delaying in order to force NHTSA to accept the cheapest fix or be charged itself with delaying the protection of motorists on the highway.

"In short, it is a quite corporate strategy designed to implicate NHTSA in any future public, congressional or judicial accusations of capability."

Claybrook said that last week Ford, with NHTSA observing, had crash-tested a Pinto with a new protective shield developed by the company.

Nader wrote Ford that the Pinto had failed "in recent unpublicized government sponsored crash test."

But Claybrook said that while the Pinto had failed an earlier crash test last week, a second test, with an additional shield, appeared to be successful.

As a result of the tests, she said, "we're hoping Ford will move quickly to get the recall underway."