UK: A "wrecking amendment" which seeks to derail the gay marriage bill will be debated in the House of Lords later.

The government's gay marriage bill for England and Wales was passed in the House of Commons last month - despite the opposition of 133 Conservative MPs.

Ex-West Midlands chief constable Lord Dear, who has tabled the amendment to refuse it a second reading, said a vote on Tuesday was "too close to call".

Meanwhile, supporters of the bill plan a rally outside Parliament.

The Marriage (Same Sex Couples) Bill for England and Wales would allow same-sex couples, who can currently hold civil ceremonies, to marry.

Religious organisations would have to "opt in" to offering weddings, with the Church of England and Church in Wales being banned in law from doing so.

It is backed by PM David Cameron, his Lib Dem deputy Nick Clegg and Labour leader Ed Miliband but was opposed by 161 MPs in a free vote in the Commons - 133 of them Conservative.
'Deep concern'

The bill, which has been criticised by some Conservative activists, is expected to face a tough passage through the Lords - if crossbench peer Lord Dear's amendment was passed it would effectively kill it.

Lord Dear has said he is not anti-homosexual but he has accused the government of pushing through a measure without public support.

Some 86 peers are expected to speak in Monday's debate with a final vote due on Tuesday.

Gay rights campaigner Peter Tatchell has organised a rally outside the Houses of Parliament on Monday afternoon.

He said everyone should be equal before the law in a democratic society.

Meanwhile, in a letter to the Sunday Telegraph, a Tory grassroots group has expressed "deep concern" about "the negative effect of the gay marriage bill on both Conservative Party morale and electoral appeal".

The Conservative Grassroots group has called on peers to reject the bill.

"It is alienating much of our core support while failing to attract new voters with under two years to go before the general election," chairman Robert Woollard wrote.

Last week, former Archbishop of Canterbury Lord Carey, warned same-sex marriage would set a "dangerous precedent" which could lead to sibling marriage or polygamy.

In an article for think tank Civitas, he said did not want to be "alarmist", but said it could logically be extended to "say, two sisters bringing up children together" or "multiple relationships, such as two women and one man".

"Ultimately, the proposed legalisation of same-sex marriage represents a paradigm shift in our understanding of marriage," he said.

Mr Cameron hopes the bill will become law soon and that the first ceremonies can take place by next summer.

The Scottish government has confirmed it will introduce a bill shortly to allow same-sex marriage.

-BBC