Rep. Raul Labrador (R-Idaho). (Melina Mara/The Washington Post)

Updated 11:23 a.m. ET

A prominent tea party-backed Republican lawmaker is spearheading a bipartisan proposal that would protect religious institutions and other nonprofit groups that don't recognize same-sex marriages from potential discrimination by the Internal Revenue Service.

The bill drafted by Rep. Raul Labrador (R-Idaho) is a "narrowly-tailored piece of legislation" that would protect groups "from discrimination by the federal government," he said in an interview this week.

Labrador said he began drafting his proposal partly out of fear that the IRS and other federal agencies might unfairly target groups that oppose same-sex marriage after the Supreme Court struck down a federal law barring gay couples from obtaining federal benefit this summer.

After the court's decision, "there were a lot of ideas about what to do," Labrador said. "Some people looked at overturning it, or doing a constitutional amendment. I looked at the immediate need, which is the protection of religious institutions and churches, so that they can continue practicing their religion as they see fit."

Asked if he had any evidence of government-backed discrimination against religious or conservative groups opposing same-sex marriages, Labrador cited a California bill that would revoke the tax-exempt status of the Boy Scouts unless they permit gay people to become scout leaders. He also cited comments by Democratic lawmakers, who have said that groups who don't recognize gay marriages should lose their tax-exempt status.

“I see it coming, it’s already happening at the state level and you’re hearing rhetoric at the federal level," Labrador said.

Gay rights groups reacted angrily to the bill Thursday, saying there is no need to provide further government protections when the First Amendment  is already designed to protect against such discrimination.

"There is no evidence that federal programs have or would discriminate against people because of their religious beliefs about marriage," said Fred Sainz, a spokesman with the Human Rights Campaign. "What is clear, however, is that this legislation would give a free pass to federal workers, recipients of taxpayer-funded grants and others to discriminate against lawfully married couples."

"This bill will set a very dangerous precedent," Sainz added in an e-mail. "Accommodating religious beliefs on marriage may only be the beginning. The bill's language makes clear that it should be interpreted as broadly as possible. Should federal workers and those who do business with the government get to turn away anybody they do not like based on religion -- unmarried pregnant women? Atheists?  Muslims?  Or even another member of their own faith with different views?"

The "Marriage and Religious Freedom Act" is co-sponsored by Rep. Steve Scalise (R-La.) and Reps. Mike McIntyre (D-N.C.) and Dan Lipinski (D-Ind.). There are about 60 other co-sponsors as well.

The bill and its focus on the IRS comes as several other lawmakers have introduced proposals designed to restrict the tax-collecting agency's powers in the wake of revelations that some officials targeted certain political groups seeking tax-exempt status for special scrutiny.

Sens. Lamar Alexander (R-Tenn.) and Johnny Isakson (R-Ga.) and Rep. Stephen Fincher (R-Tenn.) this month introduced the "IRS Abuse Protection Act," which would require the Treasury Department to notify a taxpayer in writing any time that the IRS accesses his or her tax accounts, tax returns or tax information.

But so far, no proposal designed to inhibit or more closely monitor the activities of the IRS has earned final approval by the House and Senate.

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