The US Republican Party’s national committee voted unanimously on Friday to reaffirm its opposition to equal marriage, and to urge the Supreme Court to uphold Proposition 8, California’s ban on same-sex marriage, and the Defense of Marriage Act.

At the Republican National Committee (RNC), spring meeting in Los Angeles, all 168 members of the party’s national committee voted in favour of the resolution without debate.

The resolution read that the RNC affirms “its support for marriage as the union of one man and one woman as the optimum environment in which to raise healthy children for the future of America”.

A second, and separate resolution was passed, speciifically tackling California’s Proposition 8, a 2008 state-wide constitutional amendment banning equal marriage, and urging the Supreme Court, currently considering the ban, to uphold it.

The resolution went on to mention the Defense of Marriage Act, the US federal law which currently restricts the marital benefits of married same-sex couples.

The adoption of this hardline stance goes against the direction members of the RNC’s leadership had been trying to steer the party, which aimed for a more centrist, softer position on issues such as equal marriage.

Last month, Reince Priebus, the RNC’s chairman revealed a 100-page long ‘Growth and Opportunity Project”, popularly referred to as the autopsy, which looked at the party’s lacking numbers at the polls, and the failure of Mitt Romney in last year’s presidential election.

Part of the project included a $10 million (£6.5 million) campaign to help gain the support of LGBT and Hispanic, black and Asian communities in the US. 

The autopsy read: “There is a generational difference within the conservative movement about issues involving the treatment and the rights of gay people – and for many younger voters, these issues are a gateway into whether the party is a place they want to be,” the report said. “If our party is not welcoming and inclusive, young people and increasingly other voters will continue to tune us out.”

Last week, far right Republicans wrote to Priebus to say he would lose their support if he continued to pursue the path towards centrism.

The letter read: “The Republican party makes a huge historical mistake if it intends to dismantle this coalition by marginalizing social conservatives and avoiding the issues which attract and energize them by the millions.”

Gregory T Angelo, executive director of the Log Cabin Republicans, an association of gay GOP members, had said he did not expect the party to suddenly support equal marriage, but that he was surprised by the hardline approach.

“No one was expecting the GOP to change its platform position on marriage at this meeting, but clearly those in opposition to equality feel threatened by the growing numbers of Republicans who support the freedom to marry,” he said in a statement.

Two Republican Senators have recently come out in support of equal marriage. Mark Kirk of Illinois became the second Republican Senator to come out in support of equal marriage last week, after Rob Portman, one of the original sponsors of the Defense of Marriage Act, who also recently offered his support to same-sex marriage after the revelation that his own son was gay.

“The GOP platform didn’t stop Senator Portman from evolving, nor Senator Kirk, and any reaffirmation of the party platform isn’t going to stop more Republicans from joining their colleagues on the right side of history,” continued Angelo’s statement.

Jimmy LaSalvia of GOProud tweeted his dismay at the hardline stance. He said: “Today’s anti-gay marriage resolution = more evidence that the GOP isn’t finished losing… The RNC is like the alcoholic who admits he has a problem, then continues to drink.”

Earlier this week, former US presidential hopeful Rick Santorum spoke out against the idea that the Republican Party might support equal marriage, and said it would be “suicidal” if it did.

Rock singer Kid Rock said this week that he supports equal marriage, and has spoken out to say that he was “fucking embarrassed to be a Republican”, because of some party policies.

The US Supreme Court Justices recently indicated a possible interest in striking down the Defense of Marriage Act (DOMA), as it heard arguments around the issue.

The court also heard arguments around Proposition 8, the state of California’s ban on equal marriage. Then the justices questioned the meaning of marriage, and challenged arguments for the ban. 

A decision by the Supreme Court in both cases is expected by the end of June.