British lawmakers yesterday backed legalising gay marriage in the first of several votes on the issue, after a debate that split Prime Minister David Cameron’s ruling Conservative party in two.

The draft law, which proposes legalising same-sex marriage in 2014, was carried by 400 votes to 175 votes.

The legislation is several stages away from becoming law, but has already exposed rifts within Cameron’s party at a time when he is facing growing talk of a possible leadership challenge.

Many Conservative MPs stood up in Parliament to denounce the legislation ahead of a vote in which more than half of Cameron’s 303 lawmakers (136 against and 36 abstentions) rejected the measure on moral and religious grounds, threatening a corrosive legacy of bitterness.

It was getting into “Alice in Wonderland territory” for any government to come along and rewrite the rules of marriage, Conservative lawmaker Roger Gale told Parliament, echoing the views of many in his own party.

“This is not evolution, it’s revolution,” added Edward Leigh, another Conservative MP, saying marriage was “by its nature a heterosexual union”.

In a sign of how divisive the issue has become, the Chancellor, Foreign Secretary and Home Secretary implored fellow Conservatives to back the law. Cameron is trying to perform a tricky and perhaps impossible balancing act: to reconcile his desire to show his party is progressive, while many of its members are profoundly uncomfortable with such a reform. Amid talk of a possible leadership challenge to Cameron, many Conservative lawmakers say the Prime Minister is sacrificing core party values on the altar of populism.

“He hasn’t got a lot of political capital left in the bank,” Stewart Jackson, a Conservative MP who opposes the gay marriage Bill, told Reuters. “He has to deliver some authentic Conservative policies very soon.”

Such talk is rife among some Conservative lawmakers and follows a spate of articles in the British press in which a handful of MPs raised the possibility of ousting Cameron, a prospect most commentators regard as far-fetched before the next election in 2015.

The initiative has infuriated rank-and-file party activists and a protest letter signed by 25 past and present chairmen of local Conservative associations warned that members were starting to resign over the issue.

Justin Welby, the newly elected Archbishop of Canterbury and head of the world’s 80 million Anglicans, used his first comments after being confirmed on Monday to reiterate his opposition to gay marriage.

Conservative MPs’ grievances are many: that Cameron is “arrogant”, that he is too fond of the European Union, that the party’s policies have been diluted by its coalition partner because Cameron failed to win the last election outright, and a nagging fear that he will not win the next one.

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