The Federal Aviation Administration should establish stricter passenger screening requirements and impose tougher penalties against airlines to improve the performance of airport security workers, a General Accounting Office official told Congress yesterday.

"We found that there are shortfalls in the passenger screening program," said Kenneth M. Mead, a GAO associate director. He was testifying about a GAO study that reported that security workers at 28 major domestic airports failed to detect 20 percent of the imitation weapons and bombs concealed by FAA investigators in carry-on luggage and on passengers during the last four months of 1986.

Results of the GAO study and of the FAA's security check at Washington National Airport were reported in yesterday's editions of The Washington Post.

The GAO report found that the effectiveness of security checkers varied widely, with workers at Anchorage's airport missing only 1 percent of the test objects, while screeners in Phoenix failed 66 percent of the FAA's tests, said Rep. Howard C. Nielson (R-Utah).

The 20 percent average failure rate, which matched that posted by security workers at National Airport, "is unacceptable on its face," said Rep. Cardiss Collins (D-Ill.), chairwoman of the House Government Operations subcommittee on government activities and transportation.

"The wide variation in security test results among airports reflects the FAA's misplaced trust in the airlines . . . and its failure to take enforcement action against airlines who endanger the traveling public through weak and slipshod security," she said.

The FAA, which had not compiled such information on a national basis until the subcommittee requested it last fall, argued that the GAO study of 2,419 FAA tests was inconclusive. "Their sampling is far too small to reach any meaningful conclusions," said Raymond A. Salazar, director of FAA's office of civil aviation security. "We believe, however, that an 80 percent rate is an effective deterrent," he said.

The FAA since 1973 has required commercial airlines to screen almost all passengers and carry-on baggage for weapons or explosives. The airlines hire private firms to conduct the screening with X-ray machines, metal detectors and personal searches. Each method is subject to mechanical or human error.

The FAA tests the screening process by hiding objects on individuals and carry-on luggage, but does not penalize an airline if the checkers fail the tests.

Salazar said the FAA is studying the possibility of requiring security workers to pass a minimum number of FAA tests and fining airlines if their checkers fail too many tests.

Collins said she will introduce legislation establishing such standards and penalties if the FAA does not do so within three months, because she said "the need is so apparent." "It concerns me that the honor system between the airlines and the FAA just is not working."

The FAA and GAO declined to release an airport-by-airport breakdown of their findings, citing the safety risks related to identifying an airport as having relatively weak security.

Dulles International Airport was not included in the GAO study because the FAA conducted only 10 tests there during the last four months of the year, which did not yield enough information for meaningful analysis.