WASHINGTON — Representative Barney Frank has vowed to keep transgender rights in his bill to protect gays and lesbians in the workplace, despite opposition from some key moderates that could derail the proposal.

For decades, the Newton Democrat has led congressional efforts to help gay workers, and three years ago he similarly included transgender rights in the Employment Nondiscrimination Act. But he wound up removing that provision in order to get the legislation passed in the House, a move that divided the gay rights community. That bill died in the Senate.

Now Frank says he will keep transgender rights in the current bill, and gay rights activists appear united in support.

But some Republicans say they would back the legislation only if the transgender rights portion is dropped.

“If you include transgender rights, I think that just pushes the envelope too far,’’ said Representative John Campbell of California, a Republican who voted for Frank’s bill in 2007. “It is seen by the populace as a very extreme procedure.’’

Campbell is not the only previous supporter to object. Republican Representatives Jeff Flake of Arizona, Paul Ryan of Wisconsin, and Jim Gerlach of Pennsylvania also say they don’t support the current version because it includes transgender rights. Also, some moderate Democrats have expressed concerns about voting on the transgender provision with the midterm elections approaching.

Transgender generally refers to people who are born as one gender but live as another, and gender identity refers to how individuals define their own sex.

While gay rights such as protection from hate crimes or workplace bias are becoming increasingly accepted by the public, transgender rights lag. Opponents deride laws that include transgender rights as “bathroom bills,’’ over concerns about males who identify as a female demanding the right to use the women’s bathroom.

“The right wing has correctly identified it as a really useful wedge issue,’’ said Susan Stryker, who is transgender and an associate professor of gender studies at Indiana University. “They can use it to inflame really baseless fears on the part of the general public, and they know it’s a vulnerable spot with some not-insignificant fraction of the gay and lesbian community.’’

Frank’s decision to push forward with an employment nondiscrimination bill that includes transgender individuals illustrates a gradual shift among many gay-rights activists, who say that any new civil rights should be given to all in the gay community.

But battles over transgender rights in Massachusetts and other states have shown how difficult it can be to grant such rights.

Twenty-one states offer employment protections for gay workers, but eight of those — including Massachusetts — do not extend such coverage to transgender people.

Massachusetts granted gay and lesbian individuals employment protections in 1989, but a bill that would award similar rights to transgender people remains tied up in the State House. The issue has become a flashpoint in the Massachusetts governor’s race, with Charles D. Baker and Timothy P. Cahill both saying they would veto transgender rights legislation while Governor Deval Patrick said he supports it.

Given the controversy both on the state and national level, some transgender individuals are concerned that they will eventually be left out of the congressional legislation. “Many people are concerned that [Frank] sees transgender rights as a bargaining chip, the first thing to get rid of,’’ Stryker said.

This time, Frank said, he’s committed to keeping transgender rights. The Massachusetts Democrat, who has been openly gay since 1987, has pushed for employment protections since he was a state representative in the 1970s, when some people didn’t want to think about gay people, Frank said. “To some extent, the transgender community is in that same situation, where the very mention of it makes people uncomfortable,’’ he said.

Gunner Scott, executive director of the Massachusetts Transgender Political Coalition, said his own experience shows the protection is necessary. “People still feel entitled to go up to someone they see is transgender and say really awful things in public spaces,’’ Scott said.

Frank’s measure, which has 202 cosponsors, would make it illegal for employers with 15 or more employees to discriminate based on sexual orientation or gender identity. Religious organizations and the military are exempt.

Some conservative groups ridiculed the proposal. The Traditional Values Coalition asks on its website, “Do you want men dressed as women teaching your kids?’’

Frank has tried to address such concerns by including a provision in the bill that says companies can require employees “to adhere to reasonable dress and grooming standards.’’

The Senate’s version of the current bill has 44 cosponsors, including Senator John Kerry, the Massachusetts Democrat, and Maine Republicans Olympia Snowe and Susan Collins. Senator Scott Brown, the Massachusetts Republican, has not taken a position, according to his spokesman. The Obama administration backs the measure, saying on the White House website that it “believes that our anti-discrimination employment laws should be expanded to include sexual orientation and gender identity.’’

© Copyright 2010 Globe Newspaper Company.