Campaigners for and against gay marriage are ramping up their efforts amid confusing signs about the likelihood of legislation.
Tory opponents of gay marriage, who were encouraged by the absence of any legislation in the Queen's Speech, have been stepping up the pressure to have the changes shelved.
Defence secretary Phillip Hammond has become the most senior member of the government to speak out against a change. He is backed by Baroness Warsi, who recently made a speech about the need for religion in British public life.
Children's minister Tim Loughton recently wrote to a constituent expressing his opposition to the policy, saying: "Marriage as a religious institution cannot be anything other than between a man and a woman.
"I do not see why we need to change the law, especially at this time when there are so many other important matters for the government to be addressing."
There remains strong support for the move at the top of the party, however, not least of all from the prime minister and local government secretary Eric Pickles, who last weekend said it was a "question of good manners".
Meanwhile, non-parliamentary campaigns have been ramped up as activists try to gather momentum ahead of possible legislation.
New cross-party group Out4Marriage.org kicked off a viral campaign today, modelled on the hugely successful 'It Gets Better' YouTube project designed to give support to gay teenagers in the US.
The videos which will form the backbone of the project are expected to feature politicians of all parties and celebrities "coming out for marriage".
The viral campaign should help bolster support from gay groups. Stonewall – the leading gay rights group in the UK – was initially reluctant to call for gay marriage and even now has a decidedly lukewarm approach to the issue.
Writing in the Guardian today, Archbishop of York John Sentamu said gay marriage would be unjust.
"I firmly believe that redefining marriage to embrace same-sex relationships would mean diminishing the meaning of marriage for most people, with very little if anything gained for homosexual people. If I am right, in the long term we would all be losers," he wrote.
"It is a great mistake to use the statute to give comfort and assurance. The rule of law exists to address injustices. The current difference between marriage and civil partnerships does not involve injustice, but the proposed changes arguably would, by creating two new varieties of marriage."
A consultation on the plans is currently ongoing and legislation is still set to be on the statute book before the 2015 general election.