A confidential six-month investigation by the Montgomery County Ethics Commission went public yesterday when a police officer and a County Council member who are being investigated charged that it was a politically motivated effort to harass them.

County Council member Esther Gelman and members of the county's Fire and Rescue Association have been under investigation by the Ethics Commission since April over their efforts to defeat initiatives on the 1984 election ballot that would have changed the way council members are elected, according to letters released by Gelman.

"It is a concerted effort to intimidate people," Gelman said during a recess of a County Council meeting yesterday. "We have reason to believe they have gone far beyond any scope of responsibility ever described in the county's ethics law ."

Harold W. Needham, the comission's acting chairman, refused to comment on the probe yesterday.

According to the letters released by Gelman the investigation was launched after the commission received an inquiry about the propriety of political activities of fire-rescue association members.

At issue is whether an appearance before the association by Gelman last year, during which she urged the defeat of a proposal to require elections by councilmanic districts, constituted a conflict of interest, according to the letters.

Another issue is whether association members engaged in political activities to defeat the ballot questions while working on county time.

Based on the inquiry, the commission last April requested statements from Gelman and the fire association. Gelman complied, but members of the fire association, on the advice of their attorney, demanded to see the charges before responding.

"They refused to give me a sworn affidavit of the complaint and I said we won't answer questions until we get the sworn affidavit. I'm not so sure one exists," said fire association lawyer Karl G. Feissner, who called the investigation a "tempest in a teapot."

Last July, after the association's repeated refusals to respond, the commission asked the council to authorize hiring of an outside attorney to conduct the investigation. The council approved the request without knowing the nature of the investigation, County Council President Michael Gudis said yesterday.

The case went public Monday after a council hearing on Needham's nomination for another term on the five-member commission.

Paul H. Sterling Jr., a county police officer and chief of the Wheaton Rescue Squad, charged at the hearing that Needham had told him shortly after the investigation began that the complaint was an effort to "get" Gelman. He repeated those allegations in a letter to Gudis.

Gelman said yesterday that the commission exceeded its authority by requesting funds for an outside attorney. She said no evidence of wrongdoing has been made available to her and questioned whether the commission was actually acting on a sworn complaint.

Needham's reappointment was postponed until the ethics matter has been resolved.