Gay activist groups yesterday attacked the Defense Department's policy of discharging homosexual members of the military service.

Spokesmen for the gay organizations in New York and Washington made the comments in response to a Washington Post article yesterday that said federal investigators had seized a file of names of persons with "homosexual proclivities" from a Navy enlisted man arrested last week on espionage charges.

The article reported that military investigators were checking the names to see if there were any breach of Pentagon security by homosexuals who might be blackmailed.

Charles Brydon, coexecutive director of the National Gay Task Force in New York, said the military has never documented a case of any homosexual serviceman being blackmailed into violating espionage statutes.

"The idea that someone's sexuality has anything to do with security is ludicrous," Brydon said.

He added that there wouldn't even be a theoretical possibility of blackmail if the Defense Department changed its "discriminatory policy, which forces gays to live in fear."

A court appearance is scheduled in a few weeks in cases involving two homosexual servicemen, Air Force Tech. Sgt. Leonard P. Matlovich and Navy Ensign Vernon Berg, who have challenged the military's ban on homosexuals.