David Cameron was tonight facing demands to reopen the debate on Britain's abortion laws after Health Secretary Jeremy Hunt called for the current time limit to be halved to 12 weeks.

Tory MPs opposed to the current 24-week term limit seized on Hunt's remarks to signal the start of a new push in Parliament to tighten the existing law.

But the move horrified women's rights activists who warned that such a drastic reduction could effectively prevent testing for conditions such as Down's syndrome.

hunt

Hunt wants to reduce the abortion limit to 12 weeks

The Prime Minister said the Government had no plans to legislate, although he hinted ministers would not stand in the way of MPs attempting to introduce a backbench Bill in the Commons.

Meanwhile, Home Secretary Theresa May echoed Culture Secretary Maria Miller earlier this week in suggesting she would support a more limited reduction in the limit to 20 weeks.

However, it was the intervention of Hunt, who was promoted to Health in Cameron's Cabinet reshuffle, which galvanised the debate just as Conservatives were gathering in Birmingham for their annual party conference.

He told The Times: "Everyone looks at the evidence and comes to a view about when they think that moment is and my view is that 12 weeks is the right point for it.

"It is just my view about that incredibly difficult question about the moment that we should deem life to start."

His comments were warmly welcomed by Conservative MP Daniel Kawczynski - a strong critic of the existing legislation.

"The Health Secretary coming out in favour of reigniting this debate will galvanise the caucus that exists in Parliament, cross-party, on this issue," he said.

"There will be many of us who will never stop campaigning to reduce the limit. For as long as I am a Member of Parliament, I will never give up this fight."

Fellow Tory backbencher Mark Pritchard, the vice chairman of the parliamentary pro-life group, said it was time for an "up-to-date" national debate on the term limits for abortions.

"The law currently lags behind recent scientific breakthroughs, where the survivability of young babies has increased greatly. It is time for the Government to make time for a full debate on the issue," he said.

"It is a tragic irony that at one end of a hospital taxpayers are paying for the termination of babies, whilst at the other end of the same hospital taxpayers are paying to create babies through IVF."

Professor Wendy Savage, a gynaecologist and long-standing campaigner on women's rights, expressed alarm at the prospect of another move to reduce the limit following the defeat in Parliament of the last attempt in 2008.

"The number of abortions that take place over 20 weeks is very small. Of those a considerable proportion are of foetuses which have got a congenital abnormality," she said.

"I think the majority of the population think that if somebody has got a foetus that, if born, will have a severe disability they should have the right to choose whether or not to continue with that pregnancy."

Shadow home secretary Yvette Cooper, who speaks for Labour on women's issues, said Mr Hunt had shown a "chilling" disregard for the medical evidence.

"Jeremy Hunt's statements on abortion are deeply worrying and show the Health Secretary has given no serious consideration to women's health," she said.

"Perhaps the most chilling part of his interview is the claim that 12 weeks is based on evidence when it undoubtedly is not."

Cameron, visiting the John Radcliffe Hospital in Oxford, said that while he did not agree with Hunt, he was entitled to his opinion.

He made clear that if there was a Commons vote on the issue, MPs would be free to vote with their consciences.

"On this issue all Members of Parliament - prime ministers, health secretaries, everybody - has to vote according to their consciences," he said.

"But people need to know the Government has got no plans to bring forward any legislation in this area and any vote that does happen will be a free vote.

"I personally have voted for a modest reduction from the current limit of 24 weeks because I think there are some medical arguments for that. But I don't agree with the 12-week limit and that's not the Government's policy."

Anthony Ozimic, of the Society for the Protection of Unborn Children, which campaigns against abortion, said that even if MPs did introduce a backbench Bill to reduce the term limit it was doomed to failure.

"There is a large pro-abortion majority in Parliament which will ensure that any time-limiting amendments are rejected while using the opportunity to push for pro-abortion amendments," he said.

"The real political debate about abortion in the UK should focus - as it does elsewhere in the world - on the right to life of all unborn children and on the way governments bankroll abortion access at home and abroad."