'Gay marriage a tipping point' claim grassroot Tories

Bob Woollard, chairman of the Conservative Grassroots group which organised the protest letter to the Prime Minister said: "Same sex marriage is really a tipping point, a bellwether issue if you like - people have just said 'I've had enough, I'm off, I will never vote Conservative again'.

"Scores and scores and scores of people that we have all spoken to, probably hundreds of thousands of people have said: 'I've had enough, that's it now, we can't cope with this so-called modernisation agenda'."

But a rival letter, signed by more than 100 Tory activists, called for Conservative MPs to "deal with the Bill then move on together as a party".

The Marriage (Same Sex Couples) Bill will be debated over two days, with its third reading - the final hurdle in the Commons - tomorrow.