A generation of "smart but nasty", precocious and aggressive children may be the price we pay for relying on group childcare for our pre-schoolers, says Jay Belsky, who has just been appointed to the new Institute for the Study of Children, Families and Social Issues at Birbeck College in London. He first espoused his controversial views 15 years ago, and in his latest paper, which draws on research into 1,000 families in the US, he remains unrepentant. Belsky claims that more more than 20 hours a week in group childcare - no matter how good its quality - may carry developmental risks such as less harmonious parent/child relationships, more aggression, more non-compliance and children getting along less well with their peers.

Yet good-quality childcare does have benefits for language and cognitive development, hence Belsky's claim that we may be rearing "smart but nasty" kids. Yet Belsky's interpretation of the comprehensive National Institute of Child Health and Human Development (NICHD) childcare study, which he uses to bolster his claims, is just that - Belsky's interpretation. He told the Financial Times: "The truth is, we don't have good empirical evidence to say this is the step-by-step process by which this works. It may be that a child is trying to develop a sense of the world around him, and stability and consistency with a mother figure is important to that. "Take that stability away and this may engender an inability to manage your own emotions, to develop certain social skills; and that fosters the aggression, the non-compliance, the disobedience." Based on my own empirical observation, you are as likely to see a "brat" reared by a stay-athome, full-time mother as you are to see one who has been in full-time childcare.

Belsky claims that more more than 20 hours a week in group childcare may carry developmental risks