It is more than 30 years since abortion was legalised in the UK, but the moral debate on the issue has never been resolved. After the murder of doctors at US abortion clinics, the siege against women's right to abortion continues in Britain. Last week, Care - David Alton's Christian Action for Research and Education group - launched a commission of enquiry which will attempt to prove that a foetus feels pain. This week, Frances Kissling, president of Catholics for a Free Choice, will address a meeting in the House of Lords on the subject of the Vatican's interference in issues of women's reproductive health. Yesterday, she was in Belfast (where abortion is illegal) to give moral support to pro-choice activists and help them cope with the increasingly aggressive antics of the pro-life lobby.

The abortion debate used to split down the line between those who upheld the foetus's right to life and those who believed in a woman's right to choose. Feminists and the rest of the liberal world were clear about which side of the fence they were on. They believed a woman should be able to choose motherhood rather than have it thrust upon her, so that she could give a baby, and herself, a life worth living.

Now the debate has shifted. Commentators have begun to pitch in with accounts of their own Damascene conversions, which have cast doubt on a woman's right to choose. Last year, Dominic Lawson wrote an article about the birth of his Down's syndrome baby, in which he explained why he and his wife had not tested the foetus for abnormalities. Testing unborn children for deformity, he said, was akin to Nazi eugenics. In response, Ian Hargreaves wrote an account of how his wife had undergone amniocentesis and, when they discovered that the foetus had Patau's syndrome - a condition that results in brain and heart abnormalities - she had a termination. They had to live with the decision, but as far as they were concerned, 'we took our baby's life'.

In a piece for the New Republic, new mother Naomi Wolf accused the pro-choice movement of denying the reality of abortion and lacking the moral arguments for its defence. If you feel guilty enough, she implied, borrowing the language of sin and redemption, you earn the moral right to choice. 'If one had to undergo an abortion, one could then work to provide contraception, or jobs, or other choices to young girls,' she wrote. 'One could give money to programmes that provide prenatal care to poor women.'

Wolf argues that women have become casual about abortion by their careless behaviour, they have abdicated responsibility, and therefore jeopardised their rights. They need to ask forgiveness to atone. But a woman pays heavily enough already for an abortion. She pays financially, if she is unable to secure an NHS termination with the requisite speed (for we still do not have abortion on demand). She has to justify her decision in front of not just one doctor but two in order to be certified as unable to continue with the pregnancy for physical or psychological reasons. She pays physically through the D and C, and renders herself vulnerable to future fertility problems, and she pays emotionally with guilt and grief for what might have been. She doesn't need additional burdens to purge her soul. She needs to live in a culture in which she is not blamed for her decision, but rather afforded responsibility, privacy and respect for what has to be a distressing time.

A woman has a stark choice when she finds herself unexpectedly pregnant: abortion or motherhood. A woman knows she is killing a potential life when she decides to have an abortion , but she makes that decision because she knows that she cannot give that baby a life. However unpalatable abortion may be, it is still the last safety net, preventing countless women and children from even greater potential emotional and physical damage in the future.

In Dominic Lawson's passionate and influential article, he wrote: 'Down's children are not monsters formed at random ... and yet a whole industry has been developed to make it increasingly improbable that children like Domenica Lawson will be allowed to live.' He compared the NHS policy of offering women over 35 tests and abortions for Down's syndrome to Hitler's Germany, where Nazis exterminated the mentally retarded. 'This is nothing less than the state-sponsored annihilation of viable, sentient foetuses.' But what he ignored in his heart-rending piece is the element of individual choice.

Dominic Lawson and his wife chose to refuse the tests because they wanted to bring up their child regardless of her state of health. Other couples choose to have the tests, risk miscarriage and then choose a late abortion because they cannot make the sacrifices necessary to raise a disabled child.

Medical advances have given us these choices and we cannot turn back the clock. But scientific progress has also thrown up additional moral arguments which have made it harder than ever for women to decide to have an abortion. If we now know that a foetus can feel and hear and responds to Bach, then a woman has to justify her decision to abort with even greater vehemence. But women have always found the decision to have an abortion morally difficult. They live with the responsibility that comes with that choice. It is for each individual woman to decide whether, and when, she is able to make the immense sacrifices required in order to become a mother. The fact that we now have that choice without risking death or disability should not take away the right to choose. On the contrary, it is the most important prize of all.

No form of contraceptive is infallible. People will always make mistakes and will always seek remedies. Throughout history, women have tried to get rid of unwanted children by jumping from ladders and lofts, vigorous massage, taking drugs such as arsenic and lead, and concealment of pregnancy, followed by infanticide or abandonment. Instrumental abortion without anaesthetic began towards the end of the 19th century, permanently damaging or killing many women by perforating the uterus, causing haemorrhage or introducing infection. Abortion and childbirth taken together were the second main cause of death in all women aged between 15 and 45 after TB, and the only cause of death to increase between the first and second world wars. Many deaths were concealed as 'heart attacks' or 'peritonitis', so the true figures were probably far higher. Large numbers of women lived through unspeakable horrors because they did not want to reproduce another child they simply didn't feel able to feed or have the energy to care for.

'I confess without shame,' wrote one working-class woman to the Women's Cooperative Guild in 1915, 'that when well-meaning friends said 'You cannot afford another baby - take this drug' I took their strong concoctions to purge me of the little life that might be mine. They failed and the third baby came. Many a time I have sat in Daddy's big chair, a baby two and a half years old at my back, one 16 months and one one month on my knees, and cried for very hopelessness.'

The massive rise in abortion at the end of the 19th century accompanied a profound social and cultural shift in attitude towards fertility. For centuries, children had been 'God's will' as little was known about a woman's menstrual cycle and contraception was limited to abstinence and withdrawal. Women tried to space their children from marriage to menopause, but the idea of limiting family size, of family planning, began little more than 100 years ago. Families were far larger than they are today and it was accepted that a child could die at any time - in the womb, in labour or in infancy. Children came and went, and the concept of childhood was not romanticised with the same intensity as it is today.

For hundreds of years, the assumption among doctors and midwives was that the life of a labouring woman in difficulty took priority over the foetus within. If the mother survived, she could produce another child and doctors would kill and dismember a child in the womb in order to extract it to save the mother's life. As medical advances found ways of reducing the maternal mortality rate in the thirties, medical research shifted its priorities to improving the perinatal outcome of the foetus. Scientific progress has meant that we can now see the growing foetus yawn or wave its tiny hand. We can know its gender and genetic make-up while the medics may call it a foetus, we can see that it has human features, that it is a very small baby, and that concrete image can haunt women and make the decision to have an abortion harder than ever. Increasingly, women cannot pretend that a 10-week foetus is just a blob. They have to acknowledge and take responsibility for the fact that they have killed a very young life.

There has been a massive cultural shift in our attitude to children which sadly hasn't been matched by an improvement in our respect for mothers. Every child should now be a wanted child. The idea that every child should be loved, live free from abuse and be afforded basic human rights is very much a modern concept. In just 100 years, we have moved from a society that condoned the horrors of the workhouse and child labour, to the eco-nineties in which all life is to be preserved - the calf exported for live slaughter, the fish nuked by French atomic testing and the smallest foetus, however deformed or unwanted.

We are expected to choose to have children now, and when we do so, we have to invest heavily in them and give them everything we have in order to justify that choice. Yet we are still not afforded full dignity and responsibility for deciding not to have a child, for choosing an abortion when contraception fails. A recent report from the Royal College of Obstetricians and Gynaecologists estimated that one in three pregnancies is unplanned and that in 70 per cent of these cases, contraception was being used.

'As a result of the bad old days before the Second Wave of feminism,' Naomi Wolf writes, 'we tend to understand abortion as a desperately needed exit from the near-total male control of our reproductive lives. This model of reality may have been necessary in an unrelenting patriarchy. But today, in what should be, as women continue to consolidate political power, a patriarchy crumbling in spite of itself, it can become obsolete.'

But patriarchy is still alive and kicking, and while women today do have unprecedented choice and control over their fertility, motherhood as a job doesn't get any easier and the additional emotional and psychological problems that result from that choice make motherhood harder than ever. I chose to have this child, so how can I resent the relentless toll and exhaustion from daily care and broken nights, and how can I leave a child I wanted so much to go back to work? Society, too, is less tolerant of the problems mothers face today - single mothers were pitied in the past, now they are loathed because they could have avoided motherhood altogether without a father to support them. We debate the morality of abortion, yet we belittle the problems women can face as mothers: dismissal for pregnancy, stringent maternity provisions which force many a woman back to work before she is physically or psychologically ready, chronic postnatal health problems such as urinary and faecal incontinence, a 10-15 per cent chance of postnatal depression, a substantial drop in earnings if a woman switches to part-time work or has to pay for private childcare by returning to full-time work. Most families can no longer survive on the male wage as breadwinner, most women have careers they wish to pursue and have skills to offer, yet we still see working motherhood as a luxury and a lifestyle that women have chosen and that they could have avoided if they felt they could not cope with it.

Women are still vulnerable in society because of their biology. When motherhood is unexpected or ill-prepared for, it can still plunge a woman (and her child) into poverty and despair. Modern medicine has so far failed to provide women with a safe and foolproof method of contraception, and our culture still grudgingly refuses to countenance working motherhood, or give women genuine equal opportunity, which means accommodating their biological differences from men. We see mother and baby as an inseparable unit and we insist that women make huge sacrifices in order to raise that child. We do little as a society to support the family and help women to raise healthy, happy and valuable citizens, yet we still cannot refrain from interfering in what has to be an entirely personal decision by constantly questioning the morality of abortion. It is time to stop blaming women for making difficult decisions that will affect their lives, alone. It is time we laid to rest the old chestnut of the ethics of abortion and concentrated on the considerable problems mothers face, so they feel supported in the valuable work they do. If we lived in a society that didn't punish women for being mothers, with safe, foolproof contraception and no rape or congenital malformation, then perhaps we wouldn't need abortion. But even then someone, somewhere is bound to make a mistake.

FOR

'People who are not yet parents should ask if they have the right to inflict such burdens on others'
Claire Rayner

'Faced with an unchallengeable medical diagnosis that our child had a fatal condition, I believe we were right to deploy the control that modern medicine affords'
Ian Hargreaves, former editor, Independent

'I don't believe in abortion. On the other hand, I believe in a woman's choice. So it puts me somewhere in the middle'
Nancy Reagan

'What does having an abortion say about you? That you have had sex and are therefore a loose woman, an amoral being, a failure at all the wonderful methods of contraception we have available to us? That you are an unnatural woman, a child-hater? Does choosing not to become a mother when you are single, broke, miserable, already have enough children or are just absolutely unprepared for it make you a bad person? If this is the case, then an awful lot of us are bad'
Suzanne Moore, columnist

'Abortion by permission infantilises women by seeking to deny them not only the right to choose the right course of action in the circumstances but the right to choose the wrong one. Free will is a condition of moral action it includes the right to make mistakes. The only decent, coherent and workable policy is one of abortion on demand'
Germaine Greer, writer

'In the United States, we have spawned this monster - the Right to Life Campaign. Their inability to succeed in the States and Western Europe means they have broadened their strategy. So everywhere they are chipping away at the right to abortion and in developing countries they are making sure that where it is not legal, it never will be. Like the constitutional clauses in Ireland, Brazil and also in the Philippines'
Frances Kissling, president of Catholics for a Free Choice

AGAINST

'We need to contextualise the fight to defend abortion rights within a moral framework that admits that the death of a foetus is a real death. America's high rate of abortion - which ends more than a quarter of all pregnancies - can only be rightly understood as a failure. We stand in jeopardy of losing what can only be called our souls'
Naomi Wolf

'We are the only country in the world who can prevent legal child killing. We don't need dead babies in our country. Abortion is uglier than war or mass brutality, because the baby is so helpless, so tiny'
Naimh Nic Mhathuna, chair of Youth Defence, an Irish pro-life group

'I think what I did with Roe versus Wade was wrong, and I have to take a pro-life position on choice. Women have literally been handed the right to slaughter their own children'
Norma Mcorvey, alias Jane Roe in Roe versus Wade, a 1973 Supreme Court ruling which found that a woman's constitutional right to a termination over-rode local restrictions. Mcorvey has since joined forces with pro-life group Operation Rescue

'Women who have had abortions should be forced to work in a hospital for a year to 'make amends' '
Claudia Nolte, German Minister for Women and the Family

'This is nothing less than the state-sponsored annihilation of viable, sentient foetuses'
Dominic Lawson on NHS provision of abortions to women expecting a baby with Down's syndrome

'It is worth contrasting the 1986 Scientific Procedures Act, which deals with animals and where experiments are banned even on larvae, with the lack of protection we provide for our own species'
David Alton MP

'If society puts its trust in death by permitting crimes against life, it is embracing what the Holy Father has called the culture of death'
Desmond Connell, Archbishop of Dublin

· This article was republished as part of a special edition marking 50 Years of the Guardian women's page.