Growing revolt by Tory MPs against British PM David Cameron

Downing Street will be warned by senior Conservatives that a sea change is under way in the parliamentary party as growing numbers of MPs decide that Prime Minister David Cameron is a liability, amid a revolt over the issue of gay marriage.

As unfavourable comparisons were being drawn with former premier John Major, senior figures indicated that the chairman of the Conservative backbench committee, Graham Brady, was expected to receive further letters calling for a confidence vote. Brady, who is understood to have been sent a limited number in recent months, will have to call a vote if he receives at least 46.

One senior figure said: "This is worse than John Major. There was quite a lot of sympathy for him because of the Maastricht [anti-EU] rebels. He also listened. With Cameron it feels like this could be terminal - and will be so before the election."

Cameron's flagship gay marriage policy is set to deepen the rift. The debate has sharply divided lawmakers, with Conservative former minister Norman Tebbit stoking controversy by claiming gay marriage could result in a lesbian queen giving birth to an heir by artificial insemination.

"It's a perfect political storm. It couldn't have come at a worse time for Cameron," said Iain Dale, a prominent gay radio presenter and conservative blogger.