David Cameron says he supports gay weddings in churches, synagogues and other places of worship in a move which could cause deep division in the Tories.

The Conservative party is expected to draft a bill and hold a free vote for MPs in 2013 allowing gay marriages in religious institutions but protecting those institutions from being forced to hold such ceremonies if they object.

"If there is any church or any synagogue or any mosque that does not want to have a gay marriage, it will not - it absolutely must not - be forced to hold it," David Cameron said. "This is a free vote for members of parliament but personally I will be supporting it."

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While the move to modernise the centuries-old institution of marriage may have popular support, Mr Cameron risks clashes within the party. Tory MP Peter Bone claims several cabinet ministers will vote against the move and that the Conservatives are split 50/50 on the issue.

"Despite the PM's assurance, the redefinition of marriage - because of the European Convention on Human Rights - will force churches to marry same-sex couples. This will outrage millions of people and hugely damage the government in electoral terms," Mr Bone told Channel 4 News.

"As it is a free vote, undoubtedly cabinet ministers who have expressed concerns about the redefinition of marriage will vote according to their conscience," Mr Bone said. "As for the exact split in Conservative votes, it is only an estimate, but there are clearly many Conservative MPs on each side of the argument."

Protection for places of worship

The Church of England and the Roman Catholic Church would be legally protected from being forced to host ceremonies against their wishes under the government's plans for reform but Cardinal Keith O'Brien, the UK's most senior Catholic leader, earlier this year called gay marriage plans a "grotesque subversion of a universally accepted human right".

The group Out4Marriage released a statement today saying they were delighted.

The government " appear like us to believe in religious freedom, that churches must have the freedom to decide themselves whether to allow gay couples to marry," Out4Marriage said. "We eagerly await the full details."

Downing Street and the Department for Culture, Media and Sport had no comment on the government proposal when contacted by Channel 4 News today. A report in the Pink News said reforms would go ahead despite widespread opposition by senior Anglican and Catholic leaders.

"I do not believe that it is possible to protect churches from conducting same sex marriage if other churches are allowed to do so," Mr Bone told Channel 4 News. "I think that situation would be struck down by the ECHR. No political party has any mandate for such a change."

Protests considered in consultation

Other reports said Culture Secretary Maria Miller was expected to issue the government's full response to a summer-long consultation on the plans on Thursday. Thousands participated in the consultation, including church-going protesters.

Coalition leaders have previously indicated they support the idea of equality reform, including allowing homosexual partners to have the same civil marriage rights as heterosexual couples and marry in the church or religious setting of their choice.

Nick Clegg said in an interview earlier this year that the government should not stop any church that wants to conduct gay marriage. Mr Cameron has always said there was no reason to bar other churches from voluntarily hosting same-sex weddings, providing they are not forced.