Gay marriage bill saved by Labour deal Support: Martin Brown and Archie Young embrace during a demonstration for a "yes" vote to allow same-sex marriage, outside Parliament. Prime Minister David Cameron has been forced to rely on opposition support to rescue his same-sex marriage legislation from defeat in the House of Commons. Conservative MPs had attempted to derail the Marriage (Same Sex Couples) Bill by introducing an amendment allowing straight couples to take up civil partnerships. At the moment, only gay couples are entitled to enter into a civil partnership. Ministers had warned that if every cohabiting heterosexual couple had been allowed to enter a civil partnership, the Treasury would have been left facing pension liabilities of up to £4 billion ($6.27 billion). It was thought the Treasury may have intervened to abandon or delay the legislation if the amendment was passed. The amendment, put forward by Tory MP and same-sex marriage opponent Tim Loughton, was defeated after what was described as an 11th-hour deal between Mr Cameron and Labour. The Labour leadership, who support the same-sex marriage bill, were mindful they could unwittingly ruin it by supporting Mr Loughton. The defeat of the amendment has deepened the rifts in conservative ranks, with many accusing the Prime Minister of "railroading" the controversial legislation through Parliament. And it comes at an awkward time for Mr Cameron, whose inner circle has been accused of sneering at Conservative party members. The Prime Minister sent a "personal message" to thousands of party volunteers this week, insisting that despite their differences over Europe and gay marriage, the leadership and the party had "a deep and lasting friendship." The email was sent in response to reports a member of Mr Cameron's inner circle had referred to some Conservative members as "mad, swivel-eyed loons." The Prime Minister did not refer explicitly to the remark, but said he admired and respected his party's activists. Conservative members and MPs have strongly resisted Mr Cameron's plan to allow same-sex couples to marry. Mr Cameron is relying on Labour and Lib Dem votes to steer the bill through its final Commons stage. Although he allowed his MPs a free vote, he has personally championed gay marriage and the size of the revolt represents the latest challenge to his leadership. Former defence minister Sir Gerald Howarth said gay marriage was being "railroaded through the House." "I think it is really unacceptable that a measure, which is going to have such an impact on our national life, which strikes at the heart of a thousand years of religious and cultural tradition in this country, has been reduced to a couple of hours," he said. Shadow home secretary Yvette Cooper said: "The whole debate is getting sucked into this vortex of Tory infighting, and that's making it much harder to have a sensible debate about the whole bill, which we strongly support." PA; Telegraph, London