Mayor Marion Barry indicated yesterday he saw nothing wrong with his attending a 1981 Christmas party at a 14th Street night club that features nude dancers, since there is no evidence that anything illegal occurred there that evening.

Barry quoted his minister, the Rev. David Eaton of All Souls' Church, as saying Barry was justified in serving as "the mayor of all the people," including the operators of downtown adult entertainment spots, provided he doesn't knowingly violate the law.

"I'm sworn to uphold the law," Barry said during his monthly press conference at the District Building. "But his Eaton's advice to me was that any situation which is legal in the District of Columbia, you shouldn't be defensive about the mayor's attendance."

Barry said the Dec. 22, 1981, party at "This Is It," a bar located in the heart of downtown Washington's adult entertainment district, was a "formal affair" and added:

"I have good vision and good eyes, and I didn't see any naked women there."

Barry spent a substantial part of his 40-minute session with reporters defending his integrity and broadly hinting that he and others, including Rep. Ronald V. Dellums (D-Calif.), may be victims of a nationwide effort by federal and local law enforcement agencies to "character assassinate" black leaders.

A federal grand jury has heard allegations that Dellums, chairman of the House District Committee, and some of his staff bought and used marijuana and cocaine. The House ethics committee informed Dellums Tuesday that it will investigate those allegations.

"There's a theory that you hear from time to time at gatherings of black leaders . . . that there's going to be a concerted effort on the part of either the federal government or local governments to assassinate the character of black leadership," Barry said.

"I guess the easiest way to character assassinate you is to spread rumors and unfounded truths and other kinds of things to discredit you with your constituency," he added. "It's popular now to use drugs as a character assassination process."

Barry's attendance at the "This Is It" party, one of eight Christmas parties he said he attended that night, in part caused a major flap last week within the D.C. Police Department.

D.C. Police Chief Maurice Turner sharply criticized Inspector Fred Raines, head of the department's intelligence unit, after being told by The Washington Post that Raines took three unsubstantiated police intelligence reports involving Barry to the U.S. Department of Justice last March 31, without first consulting with Turner. Raines said he went to the Justice Department to seek an outside investigation, if only to show that such politically sensitive allegations would be checked thoroughly.

Three of those raw reports, which were written in 1982 by D.C. police detectives, described allegations that Barry either used cocaine or was present while others used the drug during the Christmas party. A fourth report later on described unsubstantiated allegations that Barry had used cocaine at after-hours bars in the city.

The mayor has emphatically denied the allegations contained in the reports and said he has never used cocaine. A two-month inquiry by The Post turned up no evidence whatever that the mayor ever used cocaine or any other illegal drug.

"I've been in public office since 1971 and there's always been rumors and innuendos about everything about Marion Barry," Barry, a former school board and City Council member, said yesterday. "One thing I have great pride in is my integrity and my honesty . . . . My position has always been with reporters and with anyone else . . . let's bring forth some evidence, some hard evidence about this, or stop talking about it."

Turner said he had personally informed Barry of the allegations after he understood that the information was so unsubstantiated that no investigation was warranted. He has threatened to reprimand or demote Raines for going to the Justice Department without first checking with him.

Barry said yesterday he will stay out of the case and has asked City Administrator Elijah B. Rogers to work with Turner to decide whether to take action against Raines.

At Wilson High School Tuesday night, Barry was applauded when he defended his administration before an audience of about 200 persons attending a Ward 3 "town hall" meeting.

"The one thing you can't take from me is my integrity--I'll die first," he said.