Tabled by Conservative backbenchers Edward Leigh, Christopher Chope and Gerald Howarth, the amendment claimed that the bill on offer would create injustices for such people, despite being designed to end discrimination against same-sex couples. The attempt by Tory backbenchers to give siblings who live together the same rights as gay couples came under sustained criticism from MPs on all sides. Edward Leigh was repeatedly barracked while outlining his proposals to allow brothers and sisters who live together long term to register as civil partners in the same way as gays and lesbian couples.

Ministers, Labour and Lib Dem MPs oppose amendment

A majority of Labour and Lib Dem MPs, as well as major gay rights groups, law associations and care organisations claimed the amendment was an attempt to derail the bill and a protest against the legal recognition of same-sex relationships. It was tabled despite a similar add-on being defeated in the House of Lords earlier this year.

Ministers attacked the proposed amendment as an attempt to wreck the government's civil partnerships bill. As it stands, the bill extends to same-sex couples the legal rights over property and pensions enjoyed by married heterosexuals. It aims to stop gay people losing rights to property when their long-term partners die, and has the support of the frontbenches of all the main parties. Some opponents of the bill have said it is tantamount to sanctioning "gay marriage", though there are no religious elements in the proposed legislation.

Edward Leigh's amendment

Opening debate at the report stage today, Mr Leigh insisted he was not attempting to wreck the legislation. "All we are trying to do is ensure this bill does not create more injustices," he said. "I cannot understand, given that the bill is going to become law, given that homosexual couples are going to have these rights, why people are so violently and strongly opposed to extending these same rights to siblings." Mr Leigh said there was a "fundamental dishonesty" about the debate on civil partnerships. "This, in fact, is homosexual marriage by any other name, but the government is determined, for political reasons, not to call it a homosexual marriage bill because they do not want to alienate public opinion," he said.

He argued that it was unfair to allow gay people to inherit the home of their partner without paying inheritance tax while a brother or sister who cohabited would still be liable to pay the tax if their sibling died. Under his proposals, a 12-year cohabitation threshold on sibling civil partnerships would prevent it being used simply as a means of evading inheritance tax. He has contended that civil partnerships between siblings could also be dissolved via a simple, "paper-based" legal procedure.

Mr Leigh cited an opinion poll suggesting that a large majority of voters backed his proposal to extend the bill's provisions to siblings. "The public are overwhelmingly in favour of what we are doing," he said. "Why is it that the House of Commons alone believes it has the moral right to stand against what is a fundamental injustice?" Some 84% of those questioned by the Christian Institute said that if gay couples received financial benefits similar to those conferred by marriage, the same privileges should be extended to sisters who had lived together for 12 years or more. Mr Leigh concluded: "If we are simply, outside of marriage, creating particular groups in society with particular benefits, why only one group? Why not other groups? That is the inescapable logic of what we are trying to do today."

Mr Leigh said the Conservatives could gain an electoral boost by aping the US president, George Bush, and promoting "old-fashioned family values". The Republican party apparently benefited from opposition to gay marriage legislation in last week's US elections, with 12 states voting against its introduction.

Michael Howard supports bill, opponents vociferously oppose

Mr Leigh's measure is a watered-down version of changes agreed by peers when the bill went to the Lords in the summer. These were subsequently removed during a Commons committee stage. The Conservative leader, Michael Howard has given Tories a free vote but made it clear he will vote for gay civil partnerships. He is not expected to support Mr Leigh, who has the backing of a shadow minister, Gerald Howarth, and the former Tory chairman Lord Tebbit. Opponents to the bill were typically vociferous. Denying that she thought homosexuality was "an anathema and an abomination", Conservative Ann Widdecombe said she did think "homosexual acts are wrongful". She also called for the government to be honest and admit the bill was creating "gay marriage".

Gay Tory MP Alan Duncan' sense of 'inevitability'

Gay Tory MP Alan Duncan noted the feeling of "haunting inevitability" when debating the amendment, but said the new amendments would still "wreck the Bill by creating partnerships within an existing family which, in their confused and contradictory interrelationship, are utterly unworkable".

Jacqui Smith and Angela Eagle oppose amendment

Minister for Equality and Women, Jacqui Smith told MPs that the amendment would create legal nonsense. "Civil partnership has not been designed as a legal relationship for people who are related to each other," she said. "It is a new legal relationship for same-sex couples so that they can have the legal recognition that they cannot currently get."

Labour MP Angela Eagle was keen to point out what she felt the true motives for the amendment were. "It is invidious and divisive, but totally predictable that [Leigh] is trying to use this inappropriate legislative vehicle, first, to prove his so-called point about gay marriage, and, secondly, to wreck the bill," she said. She added that the "spinster sister" issue was an important one, but one that should not have appeared in this bill.

Gay rights groups have criticised the group of Tories trying to amend the bill. Ben Summerskill, the chief executive of Stonewall, said: "This is a transparent attempt to wreck the civil partnership bill. Sadly, it is all too obviously motivated by a dislike of gay people rather than a wish to help carers, with whom we have lots of sympathy."

The bill will now return to the House of Lords next week, where it is hoped that supporters will mobilise and ensure it is passed before the end of this parliamentary session.