Health Minister Dawn Primarolo insisted there was no evidence requiring the abortion laws to be changed.
She said: "The upper gestational limit for termination of pregnancy was set by Parliament in 1990 at 24 weeks because the scientific evidence of the time was that the threshold of viability had increased and babies were increasingly surviving at 24 weeks and above.
"That was the case in 1990 and it's certainly the case now."
Opponents of the 24-week limit say babies can feel pain in abortions
But, David Jones, a professor of bio-ethics, said research on the survival rates for extremely premature babies was "disputed".
Mrs Dorries said she believed the right of a woman to choose had its limits.
She said she reached this decision after seeing the "botched" abortion of a baby boy when she was a gynaecological nurse.
"I believe a baby has rights. Those rights kick in if that baby were born it would have a chance of life and if it feels pain as part of the abortion," she said.
'Protect the vulnerable'
Ex-minister Edward Leigh, a father-of-six, who pressed for a 12-week limit, said it would bring Britain into line with the rest of Europe.
"In modern Britain the most dangerous place to be is in your mother's womb. It should be a place of sanctity," he said.
He said "98% of abortions are social - only 1.3% are for foetuses which are handicapped, 0.4% are for risk to mother's life" and added: "It is a bleak picture of modern Britain ...I believe we should give that silent child a voice."
Labour's Claire Curtis-Thomas said she was not opposed to abortion, believing women had the right to choose.
But she added: "I can't accept that we keep the limit where it stands where there is a possibility of life. The majority of people are deeply uncomfortable with that prospect."
Labour's Chris McCafferty said restricting when a woman could have a termination "is just prolonging the agony" and was "cruel, cynical, ill-informed and inhumane".
MPs give emotive and graphic opinions on the abortion limit
"It's a basic misconception that women with an unwanted pregnancy should only enter into the actual decision-making process after counselling with someone they do not know," she said.
Lib Dem Dr John Pugh said: "There are people in our world today in no way inferior to us in capacity, intelligence and beauty who were born at 22 weeks. That ought to give us cause for reflection."
Earlier a bid to cut the limit to 12 weeks was opposed by 393 votes to 71. A further attempt to get the limit down to 16 weeks was defeated by 387 votes to 84.
On Monday night a cross-party attempt to ban hybrid animal embryos was defeated, and a bid to ban "saviour siblings" was voted down by 342 votes to 163.
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