The five major U.S. car makers say indefinite layoffs of autoworkers declined to 235,631 this week while temporary layoffs dipped to 7,200.

The decline in the indefinite rolls was attributable mostly to callbacks at American Motors Corp.'s Kenosha, Wis., plant, which is gearing up for production of the 1983 Alliance cars, the carmakers reported.

Scattered callbacks at Chrysler Corp. supplier plants and resumption of work at General Motors Corp.'s Janesville, Wis., plant prompted the decline in temporary layoffs.

Last week the automakers said 236,907 hourly workers were on the indefinite rolls, while 14,350 were temporarily idle.

GM had 141,000 laid-off workers without a recall date, unchanged from last week, and temporary layoffs dropped to 3,000 from 6,000 last week. GM has called back about 2,500 workers at Janesville, which has been down for months for model changeover, GM said.

GM, in an apparent effort to ward off a white collar unionization drive, also announced yesterday that it was returning, in effect, to its old system of basing layoffs on seniority instead of performance and instituted job security measures.

The company in a statement said it was notifying its 129,000 salaried workers in the United States of "significant changes in policies and benefit plans" that offer them job security and income protection.

Also on the automotive front, Ford Motor Co. Chairman Philip Caldwell was quoted by the Detroit Free Press yesterday as saying the No. 2 automaker will not close any additional plants in the United States this year.