The Department of Transportation asked the Ford Motor Co. yesterday to recall almost 1 million 1970-73 Ford Mavericks and 1971-73 Mercury Comets to correct a "safety-related defect" that causes a large percentage of the cars to catch fire after rear-end collisions.

Citing new data that indicates the Mavericks and Comets may be more prone to rear-end collision fires than the Ford Pinto, DOT's National Highway Traffic Safety Administration wrote Ford President Philip Caldwell yesterday to warn of the findings.

The letter to Caldwell cites DOT's "initial determination" of a safety defect and invites Ford to respond at a public meeting on May 29. Unless Ford can prove NHTSA's studies to be incorrect, such a defect finding carries with it a requirement of a recall.

In a statement issued last night from Ford's Dearborn, Mich., headquarters, Vice President Herbert L. Misch said, "We are evaluating the material received from NHTSA and will respond to its initial finding once we have completed our investigation."

NHTSA said it has received reports of at least 26 rear impact crashes involving Mavericks and Comets resulting in fuel spillage and fire and causing at least 31 fatalities and 19 injuries. The Maverick and the Comet are virtually the same vehicle. Both have fuel tanks located in the rear.

NHTSA said it had conducted an engineering analysis of the problem and found that in two of five test crashes in which 1973 Mavericks were hit in the rear by 1974 Plymouth Fury sedans at 30 miles per hour, fires started because of fuel leakage. In the other three tests, the agency found, the fuel tank was punctured and leaked from 10 to 100 ounces of fuel per minute.

Federal safety standards permit leakage of no more than one ounce of gasoline per minute after a series of barrier and rollover tests.

The Ford Pinto was the subject of one of the largest recalls in history when NHTSA determined that its gas tank had fuel spillage problems. One NHTSA official said yesterday that the Pinto problems were discovered in crashes at speeds of 35 mph, or 5 mph more than the Maverick test crashes.

Faced with an "initial determination" of a similar safety-related defect in the Pinto last year, Ford decided to recall 1.5 million Pintos voluntarily and try to fix the problem with a sheild and more support around the gas tank.

But last year, after the Pinto recall, the Center for Auto Safety, a consumer group, alleged that Mavericks and Comets were also experiencing rear-end collision fires.

In a Sept. 26, 1978, letter to NHTSA, center director Clarence Ditlow said that "analysis of our files indicates there are severe deficiencies in the fuel systems of the Ford Maverick and Mercury Comet that rival, if not surpass, the defects in the similar fuel tank configurations of the Ford Pinto and Mercury Bobcat."

Based on Ditlow's letter, which gave details of 21 deaths reportedly attributed to 1970-77 Mercury/Comet rear-end collision fires, NHTSA initiated its investigation.

The probe found fuel tank system defects in pre-1974 models of the cars that subject the tanks "to failure, rupture and dislodgement which can result in fuel leakage, fires, injuries, deaths and property damage," according to yesterday's letter to Caldwell.

Ford stopped making the Maverick and Comet in 1977, replacing them with the Ford Fairmont and Mercury Zephyr.