In a fundraising email, Brian Brown, president of the National Organization for Marriage (NOM), claimed that the Equality Act seeks to make support for heterosexual marriage illegal.

“Legislation pending in Congress would make showing support for marriage as solely the union of one man and one woman to be illegal,” Brown wrote to supporters.

Reintroduced in March with bipartisan support, the Equality Act is a federal bill that seeks to prohibit discrimination against people who identify as lesbian, gay, bisexual and transgender.

(Related: Pete Buttigieg endorses LGBT protections bill Equality Act.)

NOM was pivotal in passage of California's Proposition 8, a voter-approved constitutional amendment that defined marriage as a heterosexual union, and similar bans in other states. The U.S. Supreme Court in 2015 struck down such bans, saying that gay and lesbian couples have a constitutional right to marry.

“Under HR 5, the grossly misnamed 'Equality Act,' holding the view that marriage should only be between a man and a woman would constitute sex discrimination against someone who is gay, lesbian, bisexual or transgender,” Brown wrote.

Writing at Right Wing Watch, Peter Montgomery responded by noting that “none of this is true.”

“If the law were passed, the First Amendment would allow Brown to continue to send emails like the one he sent this week and work to get the Supreme Court to overturn its marriage equality ruling,” Montgomery wrote.