WASHINGTON (AP) _ Consumer advocate Ralph Nader took the giant American Automobile Association to task Thursday for its alleged laxity in defending consumer interests.

The national association of auto clubs performs a wide variety of services for its nearly 30 million members, Nader said. But that ''contrasts with its abdication of the consumer cause in other quite consequential fronts,'' he said.

Nader's charges came in a 10-page letter addressed to AAA President James B. Creal.

He was critical of the club for generally opposing government regulations, for example, pointing to club statements that safety and emissions rules should not be imposed without verifiable evidence of their need and value.

Nader asserted that the AAA has been weak in its efforts to encourage more recalls and said the organization has too quickly accepted as adequate industry efforts to improve fuel efficiency.

And he was critical of club support of higher speed limits, limited member involvement, its cautious position on mass transit and club activities in insurance.

Asked about the letter, J. Kay Aldous, a vice president of the Falls Church, Va.-based AAA, said: ''We don't plan to reapond other than to say that Ralph Nader is like a 17-year locust. He emerged July 1, 1971, to make the same irresponsible charges.''