Polls show support for gay marriage in France is falling, along with support for same-sex adoption and assisted procreation.
Backing for redefining marriage has dropped by 4 per cent, although it is still backed by a majority, according to a survey by a French research institute.
And the number of people who favour gay adoption and assisted procreation rights has fallen to below half, at 48 per cent, down from 53 per cent in August.
Some in the Government want the state to fund artificial insemination for gay couples.
The French cabinet has approved a Bill to legalise same-sex marriage and allow gay couples to adopt.
The French parliament will debate the Bill in January, and a vote is expected by mid-2013.
Redefining marriage was a key part of President François Hollande’s socialist manifesto.
But an opposition senator in the conservative UMP, Serge Dassault, said the bill is an “enormous danger to the nation.”
More than 1,000 mayors have signed a petition against gay marriage being legalised, along with the Roman Catholic Church who have been vocal in their dissent.
The head of the French Council of Bishops, Cardinal André Vingt-Trois, recently said gay marriage is “the ultimate deceit”.
Protests have taken place in 75 towns and cities across France.