Culture secretary Maria Miller has said Tory backbench concerns that religious groups will be forced to conduct gay marriage are "completely unfounded", as churches accuse the government of making up the policy "on the hoof".
Writing on The Huffington Post UK on Friday, Miller says she was proud to be the minister responsible for introducing same sex weddings and that gay people should be able to make a public declaration of love by getting married.
"Let me be utterly clear: under our plans no religious organisation will ever be compelled to conduct same sex marriage ceremonies," she says.
"The concern that we will is completely unfounded. Crucially, we have created a 'quadruple lock', putting into law clear and unambiguous protections.
"Yet, while it is right that we create those protections for those that don't want to conduct same-sex marriages, we must remember that there are religious organisations that do want to open their doors to gay couples. And for those that do, we must let them."
The government's move to introduce gay marriage has caused a deep rift in the Conservative Party, with at least 100 Tory MPs, including some ministers, expected to vote against the measure when a Bill is introduced in January.
Maria Miller: Why We Need the Quadruple Lock on Gay Marriage
Miller also rejects the accusation from the Church of England and Church of Wales that they were not properly consulted on the plans.
"We had a number of detailed discussions with the Church of England as we drew up our proposals and will continue to speak to them in the coming weeks," she says.
And she insists that the proposal to make it illegal for the Churches conducting gay weddings does not mean they will never be able to. "If they change their minds at a later date, and change their teaching, doctrine and Canon law then that is up to them," she says.
On Friday the Church of England accused Miller of making the policy up "on the hoof". And the Archbishop of Wales, Dr Barry Morgan, told BBC Radio 4's World at One programme that he thought the ban was a "step too far".
"I'm not saying that the Church in Wales is ready to conduct gay marriages, but it ought to be in a position to decide that for itself," he said.
During the debate on gay marriage in the Commons earlier in the week Tory MPs lined up to savage the government's plans, criticising the quadruple lock, comparing gay marriage to polygamy as well as insisting it should not be a priority at a time of economic hardship - an argument rejected by Miller.
"People have argued that same sex marriage is not an issue that should be addressed now, that the Government has more pressing concerns, such as the economy," she says.
"However I believe that we can't put issues of fairness and freedom on a backburner, that is not what we as a Government or I as an individual am about.
"Before too long all couples will have the right to marry. Marriage is the bedrock of our society. We are opening it up because being gay is not a good enough reason for the State to exclude people from it."
Yvette Cooper MP, Labour's shadow minister for women and equality, said Miller had made a "real mess" of the gay marriage legislation.
"Why are they making it expressly illegal for the Church of England and the Church in Wales to hold same sex marriages, when even senior figures in both churches are questioning it?" she said.
“The Government should rethink this before they publish the legislation. Religious freedom should be protected in the legislation. But that goes both ways. Churches that want to hold same sex marriages should be able to do so.