The Montgomery County Council voted unanimously yesterday to investigate the county ethics commission's handling of an inquiry into the political activities of council member Esther P. Gelman.

In a resolution authorizing the probe, the council directed its Office of Legislative Oversight to investigate allegations that the commission acted without a sworn complaint and that a commission member disclosed confidential information about the probe.

Council President Michael Gudis said at a news conference that the council investigation was needed to sort out the facts in the case. "If they hired a special attorney to investigate without a sworn complaint, we want to look into that as well," he said.

Robert K. Stumberg, a council attorney, said the commission would be in violation of the county's ethics law if it acted without a sworn complaint. Any member who discussed the case publicly also would be in violation of the law, he said.

If the allegations are substantiated, Gudis said, the council could remove commission members for acting improperly or, if the facts warrant, could refer the matter for criminal prosecution.

Acting commission chairman Harold W. Needham could not be reached for comment yesterday on the council's vote.

The ethics commission, whose five members are appointed by County Executive Charles W. Gilchrist, began the investigation last April based on an inquiry by someone who has not been publicly identified about the propriety of council member Gelman's efforts to defeat an initiative on the 1984 ballot that would have required the election of council members by district.

Although such investigations usually are conducted in private, the case went public Tuesday when Gelman and Paul H. Sterling Jr., a county police officer who also is being investigated, charged that the probe was a politically motivated effort to harass them.

According to letters released by Gelman, the inquiry about her activities focused on a speech she gave to members of the county's Fire and Rescue Association in which she urged the defeat of the ballot questions.

Gudis said yesterday that the council's probe may be expanded to determine if County Attorney Paul McGuckian discussed the investigation with other Gilchrist administration members.

His statement came after publication of a story in yesterday's Montgomery Journal in which Gilchrist's special assistant, Edmond Rovner, was reported to have said that he was asked by McGuckian to recommend two attorneys, one of whom was appointed special counsel.

Rovner denied making such a statement, said that he did not recommended any lawyers for the job and that he had no knowledge of the investigation before it became public.