D.C. school board candidate Dennis Sobin is offering a year's membership in an "adult swing club" in exchange for a $100 campaign contribution to him or to the Democratic candidate for Arlington County prosecutor, Brendan K. Feeley--who was unaware of the offer and disavows any connection with it.

Feeley, who is attempting to unseat conservative incumbent Commonwealth's Attorney Henry Hudson, said he was shocked and appalled when told that a local newspaper Sobin publishes, called Free Spirit, is carrying a half-page ad making the offer and using his name.

"I find it very disheartening that someone this disreputable would be supporting my candidacy," Feeley said. "I can only assume he is offering his support to me because I am running against someone he opposes.

"I've had no contact with Sobin and no wish to have any," said Feeley, who said he would return any campaign funds he received because of the ad.

The ad offers free membership to the latest incarnation of the "Playground," a club Sobin founded in 1979 as a local alternative to the much-publicized "Plato's Retreat" in New York City.

Sobin describes the club as a place where clothes and behavior are optional, where "very libertine people have the freedom of using their bodies in whatever way they wish."

The ad says that "your annual membership to Playground is now fully tax deductible when you support the political campaigns" of Sobin and Feeley. It adds that $100 checks should be made payable to Sobin's or Feeley's campaign committees and mailed to Sobin's committee. Anyone who does so would then get a free Playground membership, and checks to Feeley would be sent on to his campaign.

Sobin, an unsuccessful candidate for mayor in the last election, has also published a sex-oriented tabloid called "Met Forum" and had engagements canceled by the school system and the D.C. Convention Center because of the content of his programs.

He acknowledges that Feeley had no knowledge of the ad, but stands by his right to endorse him. Sobin added that the purpose of his effort is to see Hudson defeated.

"We just think Hudson is the epitome of repression, repression personified," said Sobin. "Feeley has said that the petty vice offenses that are now a priority would no longer get that attention. I have not talked to Brendan Feeley personally."

When asked if his endorsement might actually hurt Feeley, Sobin responded by recalling a joke about an ultra-right-wing group that wanted to see Ronald Reagan become president. The joke goes that the group told the candidate, "We can endorse you publicly or oppose you, whichever you think would help best."

"He has to regard this in the same way he would regard any endorsement. . . . He doesn't have to be a member or support that group," Sobin said.

D.C. elections and campaign finance officials said yesterday that Sobin's "FACTS for Better Education" campaign committee has failed to register with the D.C. office of Campaign Finance. Officials also said that the Sobin ad apparently violated elections rules by failing to note whether it was authorized by both candidates and by failing to state that a copy of the committee's financial report has been sent to the office of campaign finance.

Feeley said that his own research led him to believe that the ad was illegal. He added that Sobin's paper had earlier printed an ad endorsing Feeley that quoted Feeley's campaign literature and that he wrote Sobin a letter telling him to stop it.

Even Hudson, who was described in the lead editorial of Sobin's paper as "The Demented D.A.," yesterday joined in the attack on the ad, saying, "I would be most dishonest and lacking in candor to tell you I had any belief that Brendan Feeley had any involvement in this whatsoever."

Sobin, a candidate for the at-large school board seat that is up for election, founded his Playground club at a Southeast Washington location that was raided by D.C. police in March 1981. Because of that raid and other "harassment," Sobin said, the club now meets in various private homes. club at a Southeast Washington location that was raided by D.C. police in March 1981. Because of that raid and other "harassment," Sobin said, the club now meets in various private homes.