The government will set out its plans to allow same-sex marriages on Tuesday, MPs have been told.
At present, same-sex couples can have "civil partnerships" in church, but the coalition is looking at extending it to weddings.
Prime Minister David Cameron has promised a change in the law in England and Wales by the next election in May 2015.
On 10 December 2012 Culture Secretary Maria Miller told MPs: "The government should not stop people from getting married unless there's very good reason and being gay, I don't believe, is one of them."
She said churches would not be forced to carry out services if they are opposed to the idea.
Any legal challenge through the domestic or legal courts would be "negligible", she added.
Mrs Miller's comments followed an urgent question by Conservative MP Edward Leigh, who branded the proposals "highly controversial and legally complex".
Mr Leigh feared the move would "greatly increase" the chance of human rights litigation to force churches to conduct same-sex marriages against their will.
"The state has no right to redefine people's marriages. The state has no right to do that," he said.
The issue of same-sex marriage has deeply divided the Conservative party.
Some senior Conservative MPs and peers have launched a campaign group backing same-sex marriage while a number of others in the party staunchly oppose the plans.
Labour's Yvette Cooper argued that couples should be able to marry regardless of their sexuality or gender, telling the Commons: "The state should not discriminate."
The shadow women and equalities minister agreed churches should not be forced to conduct same-sex marriages, but argued that faith groups such as the Quakers should be allowed to do so.
Liberal Democrat John Leech welcomed Ms Miller's assurances that churches which do not want to conduct gay marriages would have "nothing to fear" from the legislation.