Lib Dems to vote on full marriage rights for gay couples

Party conference motion will further highlight the divisions between the members of the coalition

The Liberal Democrats are to use their first party conference in government to adopt a radical new policy calling for gay marriage.

In a move that risks causing deep divisions with both the Tory right, and the traditional Methodist wing of the Lib Dems, a motion backed by the leadership will advocate civil partnerships being "converted" into full marriage. It would also allow couples to remain legally married when one partner undergoes a sex change.

While senior figures in the party acknowledge that the move could prove divisive when it is debated in Liverpool next month, it is certain to be passed with the support of the grassroots who see equal rights as a totemic issue in the coalition.

A Lib Dem source said: "There will undoubtedly be some people that will speak against it, especially from the various religious groups. But this is something that the party as a whole has been calling for. It will be a key issue for us in defining ourselves against the Tories."

The annual autumn gathering will be under far greater scrutiny than ever before, with the party finally able to shake off the perception that policies decided by delegates will never come to fruition in government. Already organisers have received 1,000 additional applications for passes on top of the 6,000 for last year, while lobbyists, campaign groups, private companies and charities have swelled the number of trade stands from 67 to 90.

Leader Nick Clegg will miss half of the five-day conference, to represent the British government at a UN global poverty conference in New York. In his absence, the coalition policy to create "free schools" will be condemned in a debate, with unhappiness spreading over NHS reorganisation, nuclear power and proposed cuts to housing benefit and council house tenancies.

Conference organisers last night denied reports that the Tory Foreign Secretary William Hague would address Lib Dem delegates. "He is not appearing, he has not been invited, nor have any other Conservatives," a spokesman said. Instead, Lib Dem ministers, including Treasury Chief Secretary Danny Alexander, Energy Secretary Chris Huhne and Business Secretary Vince Cable will make government policy announcements.

The gay marriage motion will be voted on immediately before deputy leader Simon Hughes's keynote speech. He will use it as a sign of the Lib Dems striking a new, distinctive policy agenda on which to fight the next general election. Mr Hughes, who is bisexual, has backed the move and hopes that enshrining it into policy will put pressure on his coalition partners. The motion's supporters cite Mr Clegg's comments earlier this year to Pink News: "I support gay marriage. Love is the same, straight or gay, so the civil institution should be the same too. All couples should be able to make that commitment to one another."

The coalition has agreed to allow ceremonies for lesbian, gay, bisexual and transgender couples to be held in religious buildings. But the new policy would go further and "allow approved religious and humanist celebrants to legally solemnise and celebrate same-sex marriage and civil partnerships in places of worship".

Prime Minister David Cameron, writing in the IoS last week, signalled his support for "religious organisations to register same-sex relationships on their premises if they wish to do so".