More than 300,000 people have signed a petition against Marriage equality.
Organisers claimed that their petition had become the biggest public campaign since the 2010 election.
It highlights the support for the traditional definition of marriage as the union of a man and a woman, they said.
Earlier this month, the Government proposed redefining civil marriage laws so that the term can apply to civil unions between same-sex couples. There will be no change to religious marriage.
Senior Conservatives, including ministers, have joined Christian leaders in opposing the proposals.
The leader of Britainâ€™s Sikh organisations said the proposal was an â€śassault on religionâ€ť while the countryâ€™s largest Muslim grouping has also voiced its opposition.
I find it incredibly interesting that the churches want to have their cake and eat it too…david Cameron;s law changes only affect civil marriage…there will be no changes to religious marriages…and yet the busybodies in the churches, and yes that includesÂ SikhsÂ and Muslims have decided that they want to control civil marriage as well.