The fight against same-sex marriage has intensified with a cross-party letter from politicians opposing the coalition's proposals.
It was already clear the government's proposals to allow gay and lesbian couples to marry on the same legal basis as heterosexual couples would prove deeply divisive, across all parties in Westminster.
Now today's letter makes the extent of that opposition clear. It has been signed by 58 MPs and peers, of which 35 are Conservative. It is now thought almost half of Tory backbenchers will vote against the proposals when the government pushes legislation through the Commons in the new year.
"We are sceptical that the proposed protections will prevent the erosion of liberties of religion and conscience," the signatories declare in the letter, which is published in today's Telegraph newspaper.
"The proposed redefinition of marriage is unnecessary, given the legal rights established through civil partnerships.
"We understand some parliamentarians support freedom for same sex couples to marry, but we support a freedom from the state being able to redefine the meaning of marriage."
Prominent Tories who have signed the letter include David Davis, Bob Stewart and Nick de Bois. Three Labour MPs and two Labour peers also signed the letter.
Culture secretary Maria Miller outlined the coalition's plans to legislate in the Commons earlier this month. The proposals include a 'quadruple lock' designed to ensure the changes will not leave religious institutions – especially the Church of England – vulnerable to legal challenge from the European court of human rights.
Not all are satisfied, however. Today's letter warns the "overwhelming response" of the consultation on the issue is being ignored by the coalition, which it claims does not have a "mandate" to introduce the change.
Gay marriage was not included in the 2010 coalition agreement, but may be included in the renewed version to be unveiled in the new year.
"We recognise these are issues of conscience which will be given free votes in parliament," the letter adds.
"We will be seeking legal guarantees of the same freedom of conscience for our constituents and religious organisations to teach, preach and express a traditional view of marriage."
The letter may be a response to the Freedom To Marry campaign launched last week, backed by education secretary Michael Gove, London mayor Boris Johnson and transport secretary Patrick McLoughlin, a Catholic.
But some Conservative MPs are especially nervous about the issue as they fear Ukip is benefiting from the coalition's move.
"There was no public call to do this and yet he is pursuing headlong a policy that is going to enormously damage and split his own party, particularly in the shires," Ukip leader Nigel Farage told the BBC's Sunday Politics programme yesterday. The eurosceptic party polled 14% in two national polls published on Sunday.
Farage added: "I think gay marriage is one of those issues where attitudes in big metropolitan centres compared to the shires are very, very sharply different."
Environment secretary Owen Paterson raised eyebrows over the weekend after offering his own take on the political threat posed by Ukip.
"It's simple," he was quoted as saying. "Biddies don't like botties."