10.49pm BST

• The gay marriage bill has survived its greatest threat (so far) in its passage through parliament after Labour MPs joined with Lib Dems and pro gay marriage Conservatives to vote against an amendment tabled by Tim Loughton. The amendment would have extended civil partnerships to heterosexual couples and, although Loughton insisted he was not trying to derail the gay marriage bill, many MPs feared that his amendment would have precisely that effect. Yesterday it seemed Labour would vote in favour of Loughton's amendment. But at lunchtime Yvette Cooper said she would be advising Labour MPs to abstain (technically it was a free vote), and this evening the party decided to advise MPs to vote against after the government said it was in danger of losing. In return for Labour's support, Maria Miller, the culture secretary, said that the review that she promised into civil partnerships would start immediately. There will be further votes in the Commons tomorrow, when the bill will also get a third reading, but the government should win those easily. The next big threat will be in the Lords, where many peers are opposed to the legislation. But the Commons passed the bill at second reading with a majority of 225 and tonight Loughton's amendment was defeated by a majority of 305. The size of these majorities makes it hard to see how the Lords can block the bill.

• Miller has hinted that the review could lead to civil partnerships being abolished. Her aides have been briefing this line to journalists. (See 8.07pm.) In the chamber Miller did not explicitly float this idea, although she said that it was important "to understand what the demand is amongst those individuals who might be looking to undertake such a contractual arrangement [heterosexual civil partnership]" and that "what we are not trying to do in this bill is to create two tiers of marriage". But Labour's Kate Green indicated that her party would not accept the abolition of civil partnerships.

[A review] would ensure that they are not perceived simply as some sort of residual arrangement pending everyone moving to same-sex marriage. We can expect that many existing civil partners will want their civil partnerships in fact to continue. They don’t want to regard the history of the past nine years as a history of second best.

The fate of civil partnerships could now become an issue in the 2015 general election.

• Downing Street has been warned by senior Tories that a sea change is under way in the parliamentary party as growing numbers of MPs decide that David Cameron is becoming a liability. As Nicholas Watt reports, one senior figure said: "This is worse than John Major. There was quite a lot of sympathy for him because of the Maastricht rebels. He also listened, though he probably listened too much. With Cameron it feels like this could be terminal – and will be so before the election."

• It has emerged that two cabinet ministers, Iain Duncan Smith and Owen Paterson, voted with the anti gay marriage camp in the first vote of the evening, on a "conscience clause" for registrars. (See 9pm.)

• Cameron has written a letter to Conservative party members saying that he would never allow anyone around him to "sneer" at them. "I am proud of what you do," he wrote. "And I would never have around me those who sneered or thought otherwise." The full text of his letter is here.

That's all from me for today.

Thanks for the comments.