David Cameron has unveiled changes to his 'A-list' of priority candidates, saying there should not be the "slightest doubt" about his determination to get more women selected as would-be Tory MPs.
The Conservative leader announced that at least two of the four candidates on the final shortlists in larger constituencies must be women.
In target seats where there are fewer than 300 members, the local association will be "expected to select their candidate through an open primary".
The 'priority list' has also been expanded to around 150 members, of whom nearly 60 per cent are women.
Cameron has made the issue a key test of his leadership but has so far refused to adopt outright positive discrimination measures.
There has been disappointment at the number selected so far in winnable seats - of the 22 selections under the new arrangements seven have been of women.
The Tory chief said the initial progress had been "relatively successful".
"In my leadership campaign, I said we had to end the scandal of women's under-representation in the Conservative parliamentary party," he said.
"So in December, we took a number of steps to improve our candidate selection process in order to increase the proportion of women candidates, candidates from black and minority ethnic communities, and candidates with disabilities.
"We said that after three months, we would review progress and take any further action that may be necessary.
"Our review has shown that the steps we have taken so far have been relatively successful."
Cameron said he was "encouraged" that "real change is taking place within our party".
"But we need to go further, and we need to go faster," he added.
"So we are taking further steps today to increase the number of women candidates.
"I want to see more women candidates selected, and I want to see them selected on merit - through a proper, professional process that accurately assesses all the skills needed to be a successful member of parliament in the 21st century."
A further review of the new measures was pledged, and "if further action is necessary, it will be taken".
"No one inside or outside the Conservative Party should have the slightest doubt about how seriously I take this issue," added Cameron.
"I will make good my leadership election pledge to bring about a substantial increase in the number of women Conservative MPs. The party voted for it, and I will deliver it."
