Joan Smith: Have all the children you like: just don't get so superior about it

Every now and then you imagine that some particularly bone-headed notion has been discredited and you can get on with something more interesting - finishing a novel or buying a pair of Prada mules, for instance. But then someone commissions a survey, writes a provocative headline and once again we're having the same old debate and coming to the same old conclusion: "it" - whatever it happens to be on this occasion - is all women's fault.

This happened last week when a poll supposedly showed that the British put work and fun before having babies. I'm not sure that the ICM survey, published in The Guardian, showed anything of the sort. If someone is asked whether it's more important to have an enjoyable life or children, I'd expect them to plump for a nice life and only think about the weird assumption behind the question afterwards. It hardly justified a hand-wringing leader, bemoaning the existence of "a material culture where having babies comes second to almost anything else". Like what, for example? People would rather mow the lawn, makes pizzas and have their teeth capped than have children?

It's reactionary nonsense, driven by anxiety over the birth rate in Britain and ignoring the fact that the world's population is already too large at six billion and rising. More than 60 years ago the poet Harold Monro wrote: "How perilous life will become on earth/When the great breed of man has covered all".

He was right, but the debate is always framed in such parochial terms that I duly got a call from Woman's Hour, inviting me to take part in a discussion about whether it's selfish of women not to have children.

So it's back on the hamster wheel. As I have been saying for years, not all women (nor all men, come to that) want to have children and their motives are as varied as those of people who choose to become parents. Some feel no maternal instinct, some would rather do something else, some didn't meet the right person at the right time. Others would like to but can't. Lumping all of them together as selfish hedonists is foolish and insulting, which is why fair-minded people should have stopped doing it by now.

It's also based on a false premise, which is that people always have children from pure, unselfish motives. This is pretty hard to sustain when fertility treatment means that women in their late 50s and early 60s are sometimes able to become pregnant with donated eggs.

Only last week it was revealed that a 62-year-old British woman is seven months pregnant after treatment by a controversial Italian doctor; she will be in her early 80s, and her husband in his late 70s, when the child becomes an adult, assuming they live that long. In such cases, criticism is usually focused on the mother, sounding both ageist and sexist, but there is clearly a case against couples of this age giving birth to children in the knowledge that they may not be around long enough to bring them up.

People become parents because they want to, which I wouldn't mind if some of them didn't then go on about how much nicer they are than the rest of us just for deciding to have kids or because they've suddenly felt all these marvellous new altruistic emotions.

Since love comes in many forms, anyone who claims not to have known its true meaning until they held their own child in their arms seems to me deficient as a human being. People are welcome to have as many children as they like, as long as they don't use it as an excuse for feeling superior and it doesn't end up destroying the planet.