British PM facing revolt on gay marriage

Not only are backbenchers in the centre-right party, which governs in coalition with the smaller Liberal Democrats, likely to vote against the bill but grass-roots Tories are also turning away, newspapers said.

Reports suggested that between 130 and 200 of the 303 Conservative lawmakers will not back the bill when it is debated in parliament's lower House of Commons for the first time on Tuesday.

The Times said Conservative MPs told the newspaper that activists were resigning or refusing to renew their membership in large numbers in protest at the government's plans.

A ComRes poll of just over 2,000 people who voted Conservative at the 2010 general election, found that 20 percent of them agreed that they "would have considered voting Conservative at the next election but will definitely not if the coalition government legalises same-sex marriage".

The poll in The Daily Telegraph newspaper found that a further fifth of Conservative voters said they were unsure whether they would vote Tory again if the measures become law.

The survey also found that 62 percent of voters overall thought Cameron's chief motivation was trying to make the Conservatives seem "trendy and modern".

"This is a wake-up call to just how damaging an issue gay marriage is for the Conservative Party," former children's minister Tim Loughton was quoted as saying.

"Many stalwart Conservative supporters are feeling pretty bruised by this issue which came out of nowhere, didn't feature in the manifesto and is now being forced through by the government that seems to want to pick a fight with its own supporters."

He said grass-roots Conservatives were telling the leadership that it would not be a vote-winner at the 2015 general election.

"We need to sort the economy out in order to win the next election and gay marriage isn't up there," he said.

Meanwhile backbench Tory lawmaker David Burrowes said: "Conservative supporters did not expect the government to divide the party, divide the nation, divide church and state and divide marriage. And they won't easily forget it."

The prime minister's Downing Street office said Cameron would be encouraging colleagues to vote for the bill.

"It is a free vote but clearly the prime minister is in favour of the legislation," said a spokesman.

"He firmly believes that it is the right thing to do and of course he will encourage others to vote for it."

Cameron has also made clear that tax breaks would not be included in next month's budget -- a move some would see as appeasing malcontent backbenchers -- but would be introduced later in this parliament.

In plans unveiled in December, the government said it was proposing to allow same-sex couples to marry, but would explicitly ban the established Churches of England and Wales -- which are opposed -- from conducting ceremonies.

Other religious institutions can "opt in" if they wish.

Gay couples in Britain have had the right to enter into a civil partnership since 2005.