Speaking after an event in Redditch, Prime Minister David Cameron said:
"I'm a massive supporter of marriage and I don't want gay people to be excluded from a great institution.
"But let me be absolutely 100% clear, if there is any church or any synagogue or any mosque that doesn't want to have a gay marriage it will not, absolutely must not, be forced to hold it."
Same-sex marriage will remain illegal in the Church of England, as the Government unveiled its plans to extend marriage to gay couples.
David Cameron is facing a backlash from Tory MPs and religious groups over allowing gay weddings in churches.