What is the golden rule of modern parenting? Never criticise how someone else does it. Of course, you can indulge in the “can you believe that they fed their kids Coca-Cola for breakfast” chat afterwards. But nothing busts a friendship quicker than wading in on another mother’s mothering — or father’s fathering. Though the vexed issue of nonparental childcare comes close. There are certain yummy-mummy circles in which I am circumspect about even mentioning that I work. Conversely, I have learnt the hard way not to assume that because I am a working mother I can wade in with advice to other working mums about their childcare arrangements.

So it is with my hard hat firmly on that I come to last week’s worrying report into nursery care for the underthrees. An evaluation of a £370m government neighbourhood nurseries scheme found that toddlers spending more than 35 hours a week in daycare were prone to be more aggressive. They are more bossy, tease other children, stamp their feet, obstruct other playmates and get anxious when toys or refreshments are being handed around.

I should state here that I have two little girls, aged one and four, and have worked in an office pretty well full-time since they were born (I work one day a week at home). I was also largely brought up by nannies myself, as my mother worked. So I am not one of the “let’s bash working mums” brigade.

However, I’ve always been wary of nurseries, perhaps because my first nanny left a nursery to come and work for me and told me toe-curlingly ghastly stories of what she witnessed there. Every few hours, she said, she would have 12 small bottoms to change — the babies would be lined up in rows of three for her to deal with. It was a purely mechanical business: wiping, new nappy, next baby.

I remember her telling me this while lovingly picking up my daughter and kissing her cheek, lying her down on the mat, massaging her, tickling her tummy, blowing her kisses, laughing all the time as the familiar ritual was undertaken. “I had to leave, I just hated it that I spent the whole time filling in books for the parents about what the babies were doing rather than being able to play with them, or hug them or love them. Promise me, you’ll never send a child somewhere like that,” she pleaded.

Her vision of the industrial bum-changing haunted me long before I started reading into nurseries. The research is not complimentary. Last week’s findings are the latest in a long litany of troubling results. Steve Biddulph, for instance, found that the average child in a nursery received only eight minutes of direct face-time contact a day.

Eight minutes. Jay Belsky in the British Medical Journal found that 41% of children in daycare for over 20 hours a week were insecure, but this was true of only 26% of toddlers cared for full-time by their mothers. And last year studies showed higher levels of cortisol (the stress hormone) and proneness to attention deficit disorder in children in daycare.

Despite this, the government is urging more and more of us to put our babies and toddlers into group daycare. And millions of families are doing so. Often they choose a nursery because they feel that there is safety in numbers; that with five or so adults in attendance their child is less likely to be badly treated than if it was home alone with a nanny. Some women are worried that the child will love the nanny more than them (one woman I know gives her nannies only year-long contracts). Others say, what happens if the nanny is sick, or leaves? (Then again, if your child is ill, the nursery won’t take them, so you still have that problem.) Nurseries seem a good option and they are certainly not cheap.

So what is going on? Why are nurseries creating aggressive children? Advances in neuroscience, particularly concerning attachment and the development of the brain in a child’s early years, may provide the answers. In the first year of life, a child learns to regulate its emotions and this occurs through repeated one-to-one interaction with a primary loved and trusted carer (it doesn’t have to be mum).

The crucial thing is building up trust between child and carer through repeated actions known as “mirroring”: baby sticks tongue out, you stick tongue out. It is this interaction and the sense that they are being understood and responded to which builds the baby’s sense of containment and safety. When the baby has a bad moment and the trusted carer says “don’t worry, it’s going to be fine”, the baby finds its equilibrium without recourse to panic or major upset.

If a baby is left to deal with too much panic and fear on its own too early — because its carer is disengaged, doesn’t know it very well, or is too busy looking after many other children — its stress level gets set so that only a small amount of stress causes a large reaction. Research now shows that such infants grow up to be people much more likely to experience high levels of anxiety and depression.

In developing the infant brain, what is paramount in the first two years is for the baby to become aware that they are held in someone else’s mind. That way they learn to read other people’s emotions. When it comes to aggression, the theory is that when the known carer disapproves and says “no”, the baby wants to please them (it knows that is where the smiles and love comes from) and so stops doing it. Conversely, in a nursery with many different and semidetached carers, when someone says “no” the child has no investment in doing what that person says. The long-term effect is that the child doesn’t learn right from wrong, as it doesn’t fear that one special person’s disapproval.

Is it coincidence, the experts ask, that the quadrupling of group daycare in the last 20 years has been accompanied by a 70% rise in adolescent mental health problems? What kind of a time bomb are we creating for ourselves?

Not all mothers want — or are financially able — to be there all day, every day for the first two years. I couldn’t do it, though I have enormous respect for those who do. But this research is not saying mothers must stay at home. What it is saying is that undertwos need one-to-one care and that group daycare for babies and toddlers in terms of brain development violates the basic tenets of what makes us functional humans and able to form successful intimate relationships in adult life.

I don’t want to beat up mums trying to do the best by their children; the statistics show that a bit of nursery (under 10 hours a week) isn’t a disaster even for little ones. The children who really suffer are those at nursery 8am to 6pm five days a week. Of course, some nurseries are better than others, and kids see their parents at weekends and in the holidays, but that is not enough. Parents who are using daycare that intensively need to break it up, perhaps with a childminder or nanny some of the days. Or perhaps a rethink is needed.

Do mum and dad both need to be away from the child for so many hours? Really? When kids are small, something has to give. Your child needs you, or if not you then another consistent, loving adult. Government policy must change from “nurseries for all” to more flexible working for parents. As Oliver James has pointed out, new Labour pushes nurseries, but new Labour women themselves tend to choose nannies for their children. It is not just the government’s problem, we can all change our priorities — spend less, work less perhaps. As a society we need to get to grips with the new science and change direction. Fast.

For more debate go to www.timesonline/alphamummy

Rachel Johnson is away

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