Home Secretary Theresa May has given her backing to the campaign for gay marriage, the day after the government confirmed that all Tory MPs would be able to vote according to their own concience when the law is put before the Commons.

May is the second senior Cabinet minister to give an opinion on gay marriage this week - after a letter from Northern Ireland Secretary Owen Paterson emerged suggesting he opposed the change.

David Cameron pledged to introduce gay marriage at the Tory party conference last year, but realising this week that the issue was likely to become a major distraction for all ministers, Number 10 moved on Wednesday night to confirm that there would be a free vote in the Commons.

This could be seen as a U-turn by Downing Street, who earlier in the week said it was government policy to allow gays to marry, although in reality the government has been dithering and giving out mixed messages about whether it would whip Tory MPs for several months.

In a video for the campaign group Out4Marriage, Theresa May says: "Marriage binds us together, it brings stability, I think marriage makes us stronger. But I believe also in commitment and in fidelity in marriage, I think these are good things and we should enable them to flourish.

"That's why I believe if two people care for each other, if they love each other, if they want to commit to each other and spend the rest of their lives together then they should be able to get married and marriage should be for everyone and that's why I'm coming Out4Marriage."

Some gays took to social networks to say that Theresa May's voting record on gay issues wasn't entirely to their liking, pointing to the Public Whip website's logging of key votes she abstained from voting on.

Mike Buonaiuto, co-founder of Out4Marriage told PinkNews.co.uk: “We look forward to working with the Home Secretary and the Government as a whole to ensure that the final legal discrimination against lesbian, gay, bisexual and transgendered people is removed from the statute book.

"We are equally delighted that in just a few weeks, Out4Marriage has gained support from senior Conservatives, Liberal Democrats, Labour and Green politicians.”

The government has not said when it will introduce a gay marriage Bill to the Commons. Some gay rights groups were dismayed to find it not in the Queen's Speech earlier this month, although the government insists it's still consulting on it. Downing Street has made it clear there will be a Bill before the next general election, scheduled for 2015.