Outrage as Cameron pledges 'jobs for the girls'

Party sources confirmed he felt it a realistic "aspiration" that one in three ministers would be women by the end of the first parliament of a Tory government.

But MPs on the Right of the party warned that such positive discrimination to alter the face of the Conservatives would result in talented male MPs being leapfrogged by less able and barely-tested women.

If the party wins a majority at the next election, it will get at least 55 women into Parliament.

Potentially, that would leave just two women MPs competing for each of 36 frontbench posts - and almost four men scrapping over each remaining job.

Party supporters' website Conservative-Home said the idea was "more politically correct than anything ever proposed" by Labour, while Ann Winterton, Tory MP for Congleton, said it was "patronising".

She added: "I regret that David Cameron feels it necessary to play the numbers game rather than providing a Cabinet of talented people who can best serve the country, irrespective of gender."

Former Home Office minister Ann Widdecombe said she would have been "grossly insulted" to be given a frontbench job on such grounds, adding: "I just don't see how you can say what proportion of your government will be male or female, over or under 40, or ginger or blonde."

But Justine Greening, the youngest female Tory MP, supported the plan, saying: "I'm sure David Cameron won't be willing to compromise on the quality of the people he appoints."

With only 17 female MPs to choose from, Mr Cameron has promoted seven to his 30-strong Shadow Cabinet.

Positive discrimination in favour of women is illegal, but employment regulations do not apply to government appointments in the Prime Minister's gift.

Mr Cameron also outlined plans to reform parliamentary constituencies to make them the same size if he wins power.

On average, Tory constituencies contain more voters than Labour ones, meaning that Labour can win a majority of seats even if the Tories win more votes.