Young Tories warn of rift over gay marriage

Activists urge MPs to back plans to equalise rights as PM is accused of creating a 'disastrous mess'

David Cameron was last night given a stark warning that his plans to give gay people the right to marry will open up a rift that could undermine his leadership – and threaten the Conservatives' chances of winning the next general election.

Days before MPs vote on the Government's plan to equalise marriage rights, senior members of the party's youth wing have warned that the Tories could suffer at the polls if they block the reforms.

Seven senior members of Conservative Future (CF), backed by more than 100 young activists across the country, have written to Tory MPs urging them to respect the "quiet majority" who support controversial plans to introduce gay marriage.

The counter-offensive came after rebel Tory MPs claimed hundreds of members had already deserted the party in protest at the proposals. Grass-roots resentment was intensified after it emerged that next month's Budget would not introduce a tax break for married couples – previously touted as a concession to buy off opponents of the gay-marriage plan.

The Marriage (Same Sex Couples) Bill would enable gay couples in England and Wales to get married in civil and religious ceremonies – or convert civil partnerships into a marriage.

Leading rebels concede privately that they expect to lose the vote on Tuesday, as Labour and Liberal Democrat MPs would tip the balance in favour of the proposals. But they warned last night that Mr Cameron faced a damaging "long war" to get the move through Parliament and the party at large, as he prepared to fight the next election campaign and head off potential challenges to his authority. "Cameron has a bit of credit in the bank after his speech on Europe," one MP said last night. "But he is squandering it by imposing a proposal which was not in our manifesto and is not supported by the whole party. If he wants to keep a lid on any talk of a leadership challenge, he should drop this plan."

The Peterborough MP Stewart Jackson said the gay marriage plan had "divided the Conservative Party, alienated supporters, voters and donors and opens a legal Pandora's box which will set one group in society against another." He added: "I hold David Cameron, his arrogant disregard for the views of opponents, and political misjudgement responsible for this disastrous mess."

However, the dissident MPs will today receive a letter imploring them to step back from the brink in the interest of the party, as well as equality.

"We appreciate the anxieties of many Conservative members about gay marriage," the letter, signed by all senior CF officials, declares. "However, we are concerned that the views of a quieter but clear majority may not have been heard. We share the deeply held Conservative belief in the value of marriage... and we want the institution opened up to everyone." It adds: "The new generation of voters has moved on in its attitudes to gay people, and these are the people we must attract at the next election."

The threat of a rift comes amid unprecedented speculation about Mr Cameron's long-term future. Aides last week brushed off claims that the millionaire backbencher Adam Afriyie was being groomed as a "stalking-horse" candidate to open the way for a more realistic challenger. However, the Home Secretary, Theresa May, yesterday emerged as a potential leadership contender.