A reduction in the legal limit for abortion from 24 weeks would give false hope to the parents of severely premature infants, the minister responsible has told The Times.

Speaking before the first Commons vote on the issue in 18 years, Dawn Primarolo, the Health Minister, said that claims by antiabortion MPs that foetuses are commonly viable at 22 and 23 weeks could mislead parents. Such statements suggest that premature babies have a better chance of survival than is really the case, she said.

The House of Commons will vote next week on several amendments to the Human Fertilisation and Embryology Bill, which call for the abortion limit to be cut to between 12 and 22 weeks. Supporters argue that improving survival rates among babies below 24 weeks makes the present threshold unethical.

Ms Primarolo said that research published last week underlined that there was no scientific case for a reduction, and that claims by campaigners about viability could add to the distress faced by parents of very premature babies.

“I think that the issue is, most importantly, raising hope when the science doesn’t indicate that it should be there,” she said. “There is a danger of giving hope to desperate parents, who are in difficult enough circumstances anyway, that may not be there for them.”

The new study, led by Professor David Field of the University of Leicester, found that, while survival rates had improved significantly at 24 and 25 weeks of gestation, there had been no change at 22 and 23 weeks.

No babies born in the Trent region at 22 weeks survived at all during the study. At 23 weeks, 18 per cent of those admitted to intensive care survived to leave hospital, but this rate had not changed in 10 years.

Professor Field agreed that the abortion debate could distort perceptions. “There are a lot of families whose baby comes into neonatal care whose expectations are grossly wrong,” he said. “So I think it is a danger.”

Though the embryology Bill does not contain provisions on abortion, the Government has allocated parliamentary time next Tuesday for MPs to table amendments on the issue, on which all parties will allow a free vote.

MPs who oppose abortion plan to present several options for reform, which would cut the limit to 12, 16, 18, 20 or 22 weeks. Parliament last considered abortion in 1990, when the legal limit was reduced from 28 weeks to 24.

Amendments that would liberalise the law, by removing the requirement for abortions to be approved by two doctors, are also possible. The Times understands, however, that leading MPs who support abortion rights have decided against this, because of concerns that a cut to 22 or 20 weeks could then be presented as a compromise. They will concentrate instead on defending the 24-week limit.

Ms Primarolo’s concerns about a reduction were backed by senior medical figures. Professor Allan Temple-ton, a former president of the Royal College of Obstetricians and Gynaecologists, said: “There is no good evidence that the age of viability should be reduced. If you say the age of viability is 22 or 23 weeks, it would have implications for neonatal units.”

Gail Johnson, of the Royal College of Midwives, said: “In theory a reduction in the legal limit to 20 weeks could lead to increased use of neonatal units and more pressure on specialist care units.”

Claire Curtis-Thomas, a Labour MP and deputy chairwoman of the All-Party Parliamentary Pro-Life Group, said that it was beyond dispute that some babies survived at gestational ages below 24 weeks. “We all know that the viability of life at a very young age is very, very limited,” she said.

“But it is possible to survive at ages below the abortion limit. By reducing the limit we would at least take it below the lowest threshhold of viability.”

Abortion is one of four issues related to the Bill that are scheduled to be debated on Monday and Tuesday next week, on which MPs of all parties will be granted a free vote. The others will cover the creation of hybrid embryos containing human and animal material, the use of embryo-screening to produce “saviour siblings” suitable to donate umbilical cord blood to sick children, and the need for fertility clinics to consider children’s need for a father before starting treatment.

The Archbishop of Canterbury yesterday described the saviour siblings issue as “one of the most poignantly difficult areas in the whole discussion”.

The All-Party Pro-Life Group wrote to Gordon Brown yesterday to protest against his decision to allow Labour MPs a free vote only in next week’s debates. The Government will still impose a three-line whip on today’s second reading of the Bill, and on the final reading.

“Many MPs, including those who intend to vote with the Government, are incapable of understanding why the Prime Minister is intent on this disastrous course of action, because no amount of persuasion, whipping or sanction will make some MPs vote against their conscience,” the letter said.

The group said it expects up to 60 Labour MPs to rebel in today’s vote, though the Bill is likely to be supported by a larger number of Conservatives and Liberal Democrats.

Other provisions in the Bill include a ban on sex-selection for social reasons and the closure of loopholes that have left some fertility treatments unregulated, such as fresh sperm sold over the internet. It also permits wider use of IVF records in medical research and allows surplus embryos to be used in medical training.

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