Liberal Democrat demands for gay marriage to be legalised opened up a fresh rift with the party's Tory coalition partners last night.
Activists overwhelmingly called for same-sex couples to win the same right to a church wedding as heterosexuals, arguing that it was an essential step towards full equality of treatment for gay men and women.
Supporters of the move argued that civil partnerships, which were introduced in Britain five years ago, fall short of marriage as gay couples are barred from a full religious ceremony.
They also said that civil partnerships, which can only be carried out by specially-appointed registrars, often do not carry the same pension rights as marriages.
But parity of treatment will be strongly resisted by socially conservative Tories who believe that it would undermine the institution of marriage.
Although David Cameron is a strong supporter of civil partnerships, he refused before the election to give his support to converting them into marriages.
Lynne Featherstone, the Liberal Democrat Equalities minister, promised after the conference vote in Liverpool that the Government would "listen very carefully" to the party's demands for gay marriage to be legalised.
She said: "I am proud of the Liberal Democrats overwhelmingly supporting this motion. It underlines our fundamental commitment to equality and fairness. I hear the growing call for same-sex marriage."
The motion passed by the party would also open up civil partnerships to mixed-sex couples – a move that some critics say would be impractical because of the huge expense of giving previously co-habiting couples extra financial rights.
The Liberal Democrats called for priests, as well as other religious figures, to be allowed to conduct marriage ceremonies in places of worship.
Their motion would allow people who change sex to remain in their marriage and for gay couples married outside Britain to have their status automatically recognised in this country.
Brian Paddick, the former deputy assistant commissioner in the Metropolitan Police, who stood for the Liberal Democrats in the 2008 London Mayor contest, told the conference he married in Norway – but was regarded as unmarried in British law.
Stephen Gilbert, the MP for St Austell and Newquay, said current legislation "degrades same-sex couples to a second-tier partnership". The former MP Evan Harris said the vote would give Liberal Democrats in Government, including Ms Featherstone, the right to press for a change in the law. Dr Harris said there had been a "remarkable transformation" in the Conservative Party, but added: "We need to test that new Tory commitment to equality and this is one of the areas where we can help Lynne do that.
"We should seize the moment to push the agenda forward on full equality. There's plenty of work still to do."
Fred Dunford, from Meon Valley, Hampshire, was one of a handful of activists to oppose the move, arguing it would cost the party votes on the doorstep. "Civil partnerships give enough legal protection and in tax and inheritance rights. I do not believe that we should go as far as marriage."
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