The culture secretary has warned anti-abortion campaigners that they should not use new findings on the timing of terminations to re-open the debate on the issue as a whole.

Tessa Jowell said the government would "absolutely and categorically not" allow the research on the state of the foetus at 24 weeks, the current legal limit, to change the law in principle.

While she recognised that improved science and technology could lead to a revision of the 24 week limit, this would be as far as any debate went, the Cabinet minister said.

Jowell insisted that the landmark 1960s legislation would remain in place, despite calls from some campaigners for the whole issue to be looked at again.

"I think that the principles of the 1967 Act represent a pretty broadly accepted settlement in relation to what is a very difficult issue," she told the GMTV Sunday Programme.

"I would not want to see the 1967 settlement altered. However, the original limit for late abortion was 28 weeks that's now been brought back to 24 weeks and it's right on practical grounds obviously as medical developments advance to keep those limits under review.

"It also underlines the importance of women of all ages having quick access to advice very early on in their pregnancy. So I don't think that the basic settlement alters, I think it’s right that decisions about late abortion are kept, if you like, in line with developing technology.

"But I think it's also important to remember that mercifully and because advice and help is available at an early stage that relatively few abortions take place very late and they usually take place for catastrophic reasons. For no woman, at any age, is abortion a decision which is taken lightly."