Security guards at Dulles International Airport fail to recognize pistols hidden in carry-on luggage in almost 25 percent of the spot checks conducted by airlines, congressional sources and airline officials said yesterday.

Lawrence Peer, the Federal Aviation Administration official responsible for assessing security at Dulles, told members of the House government activities and transportation subcommittee yesterday that earlier this year he rated security at Dulles "marginal" and last year described his agency's commitment to security measures there as "mediocre."

In addition, FAA officials acknowledged that as many as 25 percent of the 9,000 identification badges issued to employes at Dulles cannot be accounted for. The identification badges allow people access to areas at the airport from which the public is restricted.

"This is an extremely dangerous situation," said Rep. Cardiss Collins (D-Ill.), the subcommittee chairman. "How in the world could they permit these weaknesses to persist?"

FAA regulations require that airlines periodically test the people screening departing passengers and baggage by trying to sneak forbidden objects, such as guns, onto their aircraft. The screeners are employes of private security firms and are not required to have any formal training for their duties, he said.

Although screeners failed about 25 percent of the security tests that were given at Dulles, congressional sources and transportation officials working at Dulles said the airlines did not report the names of the workers who failed to spot the weapons.

Collins said that she called the hearing on security at Dulles because as one of two airports owned and operated by the federal government -- National Airport is the other -- it should serve as a model for all airports in the country.

Testimony from FAA officials and a representative from The Wackenhut Corp., the private security firm that screens passengers at Dulles, attributed security problems to high turnover rates, poor pay and minimal training.

"There are no educational requirements, or previous training that I can see would be specific to the job," said Betty Buttolph, facilities supervisor for Wackenhut at Dulles.

She said that she requires new employes to work for three days with a more senior person before they can work without special supervision.

She acknowledged that a test provided by the FAA and administered to all new Wackenhut employes, is never graded, and that after watching the 27 slides in the test -- examples of what luggage looks like when it passes through airport X-ray machines -- workers effectively have completed their training.

Buttolph said that due primarily to low pay -- screeners start at $3.75 an hour and earn no more than $4.20 hourly -- the annual turnover rate among her staff is about 30 percent. She said that because of Dulles' location, most companies there have trouble recruiting qualified staff.

"If your people make mistakes due to overwork, or minimal supervision," said Rep. Tom Lantos (D-Calif.), "we may have a major tragedy on our hands."

FAA officials, noting that the security program was introduced to prevent hijackings, said that there has not been a hijacking or any other violent incident on an aircraft at Dulles since it opened in 1962.

"The system is a good one," said Anthony J. Broderick, associate FAA administrator for aviation standards. "It is not perfect, but no system is."

Largely in response to increased fears of terrorist attacks, the FAA has doubled the size of its security budget in the past two years, he said. "This is not a static system. When threats change we will change directions."

Dulles has grown faster than any U.S airport over the past year, jumping from 3.4 million passengers in 1984 to almost 5.1 million in 1985.

Since Peer's most recent evaluation, the FAA has moved to improve security at Dulles, officials said yesterday. A new $100,000 identification system is nearly completed and all employes there will be issued new IDs.

The police commander at Dulles, Capt. Thomas Holderness, testified that it was not uncommon for deer hunters to slip through the airport's 27 miles of fences and on to the 11,000-acre government facility.