The U.S. Senate has voted to permit private volunteer organizations in the District such as Big Brothers to set their own policies on whether to allow homosexuals to serve as mentors for minors.

The amendment to the D.C. Appropriations Bill, introduced by Sen. William L. Armstrong (R-Colo.) and passed by a voice vote late Wednesday, was immediately lambasted by local homosexual-rights groups and city officials, who attacked it as unnecessary intrusion on city affairs.

"It's just plain wrong that the District of Columbia forces private volunteer groups to unite adult homosexuals with minors as companions and role models," Armstrong said. "Many charitable organizations, and Big Brothers in particular, provide emotional and spiritual support for troubled youths. Sensitive, impressionable children should not have as mentors and role models individuals who are historically, and correctly, regarded as unsuited to that particular kind of work.

"Yet the District of Columbia, with its so-called 'Human Rights Act,' has sought to impose that fate on these young people," Armstrong added.

Peri Jude Radecic, legislative director at the National Gay and Lesbian Task Force, said "Armstrong is preying on people's misconceptions about gays and lesbians."

The Senate is expected to vote in the next few days on the entire appropriations bill, which then goes to a conference committee for reconciliation with a House version, which has no similar amendment.

The admendment is the second attempt by Armstrong to legislate limits on gay participation in District organizations where they would serve as mentors for minors. In March, the senator offered a similar amendment to the National and Community Service Act. That proposal, which would have allowed organizations to exclude homosexuals from working with young people without explanation, was narrowly defeated.

Armstrong's actions stemmed from a decision last year by Big Brothers of the National Capital Area to allow homosexuals to serve as youth counselors when the arrangement is approved by a youth's mother or guardian.

Desiree Griffin-Moore, executive director of the local Big Brothers, said her organization has never asked Armstrong to offer the legislation. Until last year, the group automatically rejected gay men as participants. Last summer, a gay man filed a complaint with the D.C. Office of Human Rights, contending that Big Brothers was discriminating against him.

The complaint was settled when the organization changed its policy. "So far, the policy has worked," Griffin-Moore said, though she said she did not know if any gay applicants had been matched with "little brothers."

Armstrong also was behind an amendment to the D.C. Appropriations Bill for fiscal year 1990 that forbade the city to enforce its gay rights law against educational institutions with religious affiliations, such as Georgetown University, which had prohibited gay groups from holding events on campus.

"He's busy, isn't he?" said Loretta S. Caldwell, director of the D.C. Department of Human Rights. "This amendment diminishes the protection of an individual under the Human Rights Act."