Unfounded rumors that Somerville Mayor S. Lester Ralph was arrested for sexual assault have persisted as a result of an organized campaign to discredit the mayor, John Kerry, assistant district attorney of Middlesex County, said in a press release issued Tuesday.

'The Basest of Human Behavior'

Kerry stated in the press release that because rumors of Ralph's sexual misconduct persisted through this week, "the conduct of people calling the news media in an anonymous and organized fashion telling details of an incident that never occured is positively reprehensible--it is the basest of human behavior."

The rumors began when a 29-year-old man told Somerville police early on October 20, that Ralph had sexually molested him, John J. Prior '78, member of the Committee to Elect Gene Brune Mayor, said Wednesday.

The man who charged Ralph with sexual assault admitted several hours after making the charge that he had lied, Kerry stated in the press release.

Kerry also stated that a polygraph test administered to the man after he had withdrawn the charge confirmed the charge was false.

Bruce Edmonds, administrative assistant to Kerry, said yesterday, "We have seen nothing to warrant further investigation" of the alleged effort to discredit Ralph.

In a press released Ralph issued on Tuesday, the mayor said he is "unconvinced that Chief of Police Thomas J. O'Brien fully protected my rights as an individual" in handling the assault charge. He added that he would assist the district attorney's office in investigating the Somerville Police Department's handling of the case.

Ralph also said he would support the district attorney in investigating the motivation behind the "slander," and in prosecuting the individuals responsible for it.

Prior said the rumors of Ralph's sexual misconduct spread throughout Somerville and to the news media within hours of the initial charge, before the mayor had been notified of the charge.