Couples will be allowed civil partnerships from December

Alan Duncan, the first openly gay Tory frontbencher, said it was "contemptible" some councils were trying to block the civil partnerships.

He argued that harking back to a past which never really existed would lose votes in towns and cities.

Mr Duncan withdrew from the leadership contest earlier this summer.

But in a platform speech on Monday he will continue his appeal for the Tories either to change their image and appeal to young voters or face staying in opposition.

Even now there are still some Tories who do not realise how off-putting their behaviour can be, he will say.

'Get real'

Mr Duncan will say the Civil Partnerships Act helps thousands of gay couples who feel they suffer from discrimination, but it does not undermine "conventional marriage".

"It is therefore contemptible that after it was passed so overwhelmingly in Parliament some Conservative councils are now trying to block its ceremonies on council property," he will say.

"Carry on like that and this party will look like nothing more than a repository for prejudice and spite. I say to them, please, get real. So we can all get going."