The number of people responsible for monitoring the quality and reliability of work done for the National Aeronautics and Space Administration has been cut 71 percent since mid-1970, a rate more than double that of reductions in the overall agency work force, according to NASA figures.

The cutbacks could be the "common denominator" in a series of recent failures for the space program involving different contractors and different systems, according to Sen. Albert Gore Jr. (D-Tenn.), whose office obtained the figures in preparation for a hearing today and supplied them to The Washington Post.

Reductions in "quality assurance" personnel have been cited repeatedly by space program critics as a contributing factor to NASA's current problems, but this is apparently the first time the cutbacks have been added up and documented.

The quality assurance office at NASA is charged with providing independent expert inspectors to look over the shoulders of workers at NASA centers and at contractor plants who build, repair, handle and test flight hardware. These inspectors are supposed to make sure work is done properly and inform top agency officials of problems.

The revelation follows other reports documenting instances of sloppy workmanship, waste, mismanagement and related problems in the space program, still reeling from the Challenger shuttle accident on Jan. 28 and the failure last Saturday of a Delta rocket at Cape Canaveral.

Analyzed center by center, the figures show that quality assurance personnel were cut most radically at Marshall Space Flight Center in Huntsville, Ala., which is responsible for the space shuttle's propulsion systems. The number at Marshall went from 615 people to 88, a reduction of 86 percent.

Marshall officials supervised the development and production of the shuttle's solid rocket boosters. A failure in a seal on one of the rocket joints is believed to have caused the destruction of Challenger on Jan. 28 and the deaths of its crew of seven. There is no evidence that the failure was caused by faulty workmanship, though NASA officials have said that a booster joint may have been damaged during assembly before the flight.

Dr. Milton A. Silveira, NASA chief engineer, said the figures came from a report prepared as part of a campaign by some employes to get NASA to beef up the quality assurance staff.

He acknowledged that there had been drastic cuts and said they meant, among other things, that one level of testing on flight hardware failures was eliminated. In the past, the quality assurance workers performed a failure analysis to supplement that done by those responsible for the hardware program. Now quality assurance inspectors "look it [the analysis] over and sign off on it," Silveira said.

He said there were mitigating factors that accounted for some of the reductions. Some people previously classified in quality assurance at Marshall and at the Goddard Space Flight Center in Greenbelt have been reclassified under another label, he said, but he does not know how many.

Some cuts came about as part of the overall agency budget and personnel shrinkage that took place as the Apollo moon program was phased out and the leaner shuttle program began, in the early 1970s. The NASA work force has dropped from 36,000 to 22,000 since then.

And some were pulled out of contractor plants as an efficiency move and NASA relied on inspectors provided by the Defense Logistics Agency and the Department of the Air Force, he said.

Where several agencies are involved in a single plant, he said, often one agency provides quality assurance inspection for all.

"At Thiokol, for example, we use the Air Force plant representative to do most of our inspection in there, because he's there anyway," Silveira said, referring to Morton Thiokol Inc., maker of the solid rocket boosters.

The revelations come as the Senate space subcommittee, of which Gore is a member, planned today's hearing on NASA's budget authorization, with the associate administrator for space flight, Richard H. Truly, and John Brizendine, head of NASA's safety panel of outside experts, scheduled as witnesses.

Gore said NASA officials had initially informed him that the quality assurance figures did not exist. He obtained the figures following the explosion last Saturday of a Delta rocket as it was launched from Cape Canaveral, he said.