Recalls of vehicles for safety-related defects increased 18 percent last year, according to new figures released by the National Highway Traffic Safety Administration.

Domestic and foreign manufacturers brought back 7.2 million cars, trucks, vans, buses and motorcycles, compared with the 6.1 million recalled in 1983. U.S. manufacturers brought back 6.2 million vehicles last year in 125 product-safety campaigns, while foreign makers brought back 938,000 vehicles in 39 recall programs.

Most of the recalls were voluntary -- that is, undertaken without NHTSA having to seek a court order.

NHTSA, however, says that nearly 4.5 million of the vehicles recalled last year were brought back as a result of the agency's "influence." That means that NHTSA initiated safety investigations or took other nonjudicial actions to persuade the manufacturers to bring back their vehicles.

Since NHTSA began keeping recall records in 1966, vehicle manufacturers have conducted 3,707 product-safety campaigns, affecting 112.8 million vehicles. Seven of those campaigns were forced by court action. NHTSA is now involved in an eighth case -- an effort to force General Motors Corp. to recall 1.1 million model-1980 X cars.

The X cars in question allegedly have defective rear brakes that can lock if a car has to come to a stop too quickly, causing loss of driver control. NHTSA has filed a $4 million lawsuit against GM in the case, which is being heard in U.S. District Court here. The nonjury trial before Judge Thomas P. Jackson began last March 13 and is scheduled to resume Feb. 11. HIGHER GEAR . . .

Richard E. Burdette, NHTSA's former director of public and consumer affairs, has taken a new job as acting deputy assistant secretary for public affairs for the Transportation Department, which oversees NHTSA. Burdette is expected to get the job permanently, which will put him in the No. 2 job in DOT's public information office.

The promotion means that Burdette moves from the fifth to the 10th floor of the DOT building, but in terms of decor that may not be a step up -- at least for the near future. Carpets on the 10th floor were soaked with water yesterday because of water pipes that burst in the building during last weekend's deep freeze.

Burdette replaces Fred Quinn, who is moving to the Voice of America in a capacity yet to be determined. Career civil servant Barry W. McCahill will take over Burdette's old NHTSA job on an acting basis until the administration can fill the job with a political appointee.