David Cameron has challenged the membership of the Conservative party before to take on positions that may have been unthinkable in years gone by – and, in the main, he has taken the party with him. But his decision to announce, while giving evidence to the Speaker's Conference, that he wants to impose all-women shortlists on some local associations from 2010 has been met with almost universal opposition. Indeed, I hope that the force of the opposition shown to the proposal will persuade him against going down this route at all.

Among the most vociferous opponents in the party to all-women shortlists are some of the best-known female Conservative MPs. Leading the charge, in a blog post on ConservativeHome this morning, is Mid Bedfordshire MP Nadine Dorries. She rightly makes the point of principle that any female MP should know that she got to the Commons on merit and under the same rules as male colleagues – and not because of her gender.

Meanwhile, Ann Widdecombe was raising similar arguments, making the point that it is strange to be picking a fight with the party at this stage in the electoral cycle, when it is on the cusp of gaining power.

The grassroots response has also been overwhelmingly hostile to the proposal. Tim Montgomerie and I at ConservativeHome took the rare step of posting a jointly signed editorial on the site yesterday to demonstrate a united front – and you only have to look at the comments posted below that piece to comprehend the sheer strength of feeling of activists around the country on this one.

At a very basic level, it is un-Conservative and against the spirit of the meritocracy in which Conservatives believe to impose a shortlist where candidates are chosen not because of their ability, but because of a particular characteristic, be that their gender, sexuality or ethnic background.

But it is also worth noting – as I did on last night's BBC 10 O'Clock News – that imposing all-women shortlists does not sit at all easily with the party's stated commitment to localism. How can we convincingly talk about devolving power to people and lower tiers of government (a policy we are correctly pursuing) while simultaneously allowing the party to centralise power and dictate from on high when it comes to candidate selection?

It is a particular shame that Cameron is seeking to push all-women shortlists now, since the party has actually made such great progress on selecting more women without having to resort to this form of discrimination. Over the 90 or so years that women have been eligible to sit in parliament, only 66 women have ever sat as Conservative MPs. If the party wins enough seats to see a Conservative majority in the Commons, that figure will almost be matched in one parliament alone.

As a matter of fact, women are being selected in roughly equal proportion to the number of women on the candidates' list – and there are already many excellent women who I expect to enter the Commons as Tory MPs next year. It would therefore be an affront to the principles of meritocracy and democracy if another handful is seen to be joining them only because of special measures.