The Conservatives are under fire after a front-bencher said bed and breakfasts run by Christians should be allowed to turn away gay couples.

Shadow home secretary Chris Grayling said hotels should not be allowed to discriminate against homosexuals, but he suggested that individuals should have the right to decide who stays in their home.

The comments to a meeting of the Centre for Policy Studies thinktank sparked anger among gay rights activists and may prove embarrassing to Conservative leader David Cameron, who has made much of his party's increased openness to homosexuals.

Gay rights campaigner Peter Tatchell said: "David Cameron needs to clarify whether he agrees with Chris Grayling that B&B owners should have a right to turn away gay couples. Mr Cameron's silence is worrying. Many voters will be disturbed by his failure to swiftly disown Mr Grayling's support for anti-gay discrimination."

Business Secretary Lord Mandelson said: "When the camera is on they say one thing, but when the camera is off they say another. David Cameron had advertised great changes about the Conservative Party. He says they have re-thought, they have made all these sorts of changes, they are now a modern party. You turn the camera off and you find that they speak and think quite differently."

Mr Grayling said: "Any suggestion that I am against gay rights is wholly wrong. It is a matter of record that I voted for civil partnerships. I also voted in favour of the legislation that prohibited bed and breakfast owners from discriminating against gay people."

The row comes shortly after a B&B owner in Cookham, Berkshire, was reported to the police for refusing to take in a gay couple as guests on the grounds it was against her Christian principles.