Ministers have faced calls for a fresh look at abortion time limits which have not been considered since 1990.
More than 60 MPs have now signed a Commons motion backing a review after scientific and medical changes.
But Health Minister Caroline Flint said the issue was unlikely to be revisited. Ultimately, though, it is down to MPs.
Science and technology committee chair Phil Willis said the issue should be looked at again, warning it was unwise to ignore changing circumstances.
Lib Dem spokesman Evan Harris said there should be a full Parliamentary debate, although he was sceptical advances had brought foetus "viability" to under 24 weeks.
"I don't know the answer and I think Parliament should have the opportunity to see the science before advancing," he added.
Shadow health secretary Andrew Lansley agreed that abortion limits must be debated.
He called for a free vote on all sides in the event of any legislative reform.
Technological advances
Last month the head of the Catholic Church in England and Wales reopened the abortion debate by urging the government to change the law.
Cardinal Cormac Murphy-O'Connor has called on ministers to lower the 24-week abortion limit at a private meeting at the Department of Health.
He wants a joint committee of both houses of parliament to review the 1967 Abortion Act.
Cardinal Murphy-O'Connor argued that technological advances meant the abortion laws are outdated.
Modern medicine can now ensure the survival of some foetuses born before 24 weeks' gestation.
Doctors debated the issue at their annual conference last year for the first time since 1989 but voted against calling for a reduction in the limit.
Health Secretary Patricia Hewitt has already said this year she is not in favour of lowering the limit despite France, Germany and Italy setting the limit at between 12 and 13 weeks.
Downing Street has said the prime minister believes the abortion laws are a matter for individual MPs rather than the government.
Recent figures show more 185,000 abortions were carried out in 2004, but only 124 were carried out at 24 weeks.
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