Passing gay marriage rights would make gay voters more likely to back the Tories.

Maude: Gay marriage will make us electable

Maude: Gay marriage will make us electable

By Ian Dunt

Pushing ahead with gay marriage is the only way to make the Conservative party acceptable to metropolitan voters, Francis Maude will say today.

The Cabinet Office minister will insist that the move, which was branded "grotesque" by Cardinal Keith O'Brien on Sunday, will show the Tories are in touch with modern Britain.

"The Conservative party will always suffer if it is seen as if it is trying to turn the clock back to an imagined golden era," he will say at a speech to Policy Exchange later.

"You can't drive policy looking through a rose-tinted rear view mirror. If we are seen as being defined by backward looking social attitudes we will be seen as unacceptable and unelectable.

"We shouldn't arrogantly assume we always know best and that society should conform to our expectations rather than us adapting to evolving social norms."

Mr Maude will explain how his brother's death from Aids convinced him that Section 28, a Thatcher-era prohibition on the "promotion" of homosexuality in schools, prompted many members of the public to conclude the Tory party was hostile towards them.

"To survive and succeed over the centuries it has had continually to modernise and evolve. When we have failed to do so – when we failed to understand and influence the spirit of the age – the electorate rightly punished us," he will add.

"We are the party that sent the first female MP to Westminster; and we are of course the party of the first female prime minister. We legislated to introduce women peers into the upper chamber and in government now we will legislate to introduce same-sex marriage."

David Cameron won a warm round of applause when he celebrated gay marriage at last year's Tory party conference, convincing many observers that the rank-and-file would be comfortable with the move.

But some backbench MPs, most vocally Peter Bone, have complained about the consultation.