AS A 22-year-old university student in my final year, I lived in a shared house that overlooked a primary school. On the days when I was not in college, but in my room, "studying", I would sometimes spend playtime (theirs, not mine) at my window, watching the children enjoy what my mother would have called their "mad half-hour".

It was endlessly fascinating, and as instructive about human behaviour as Sir David Attenborough has found the observation of meerkats or gorillas to be about the animal realm.

A decade and a half later, I would often enjoy a similarly innocent experience while supervising my own son in the local playground. Until, that is, two police officers approached me on the perimeter one day, and asked why I was there. In that moment, suspicion supplanted innocence, and a law-abiding parent was transformed into a police suspect.

It was a sign of things to come. Mandatory CRB checks, for example, have forced everyone - from cathedral flower-arrangers to authors visiting schools - to prove their innocence in anticipation of any crime. As Ian Huntley proved in Soham, however, real criminals (aided and abetted by police oversight) have ways of evading detection.

Nor is this an isolated instance of the principle of unintended consequences. Government proposals to have all children visiting A&E departments registered on a child-protection database make potential criminals of every responsible parent, while simultaneously encouraging actual abusers to stay clear of hospitals, where rescue could be at hand.

And, come the Queen's Speech in June, there is arguably worse ahead. A so-called "Cinderella Law" is to be included, which is designed to protect children from "emotional" abuse by threatening parents with prison (and the removal of their children into care) if they are judged guilty of harming a child's "intellectual, emotional, social, or behavioural development".

With what qualification - or, indeed, justification - a modern Solomon is expected to arbitrate on so complex and nuanced a thing as child-rearing is not clear. Nor is it clear at what point prosecutions will begin or end.

There will be no shortage of people arguing, for instance, that clear "emotional, social, and behavioural" damage is done by sending a child to boarding school at the age of eight. They might further argue that a single working mother is guilty of a similar dereliction of love and affection when she hands over her children to a child-minder, instead of staying at home with them all day.

The articulate middle classes will doubtless find the wherewithal to argue their way out of these "charges" - a proportion of which, statistically, will be brought by nosy neighbours or malicious former partners. But the less fortunate, those in real need whose family life is rough round the edges, but no less loving at the centre, could well find themselves the object of unwelcome visits by an army of paid professionals who once visited homes to help rather than to pry and to judge.

In all but the most extreme cases, separating a child from his or her mother is arguably itself a form of cruelty. It risks punishing a woman for sometimes simply not being able to cope, and offers mere care to a child who craves love - the absence of which will make inadequate parenting more likely in the future, not less.

If the state has to become the interfering nanny who knows best, it is arguably better that it intervene as a helper and educator rather than a latter-day witchfinder general, sniffing out crimes where they may not exist. Paid witchfinders have to justify their post by finding witches in the first place, and, in the jargon of the day, meeting their quotas.

Trevor Barnes reports for the Sunday programme and other BBC Religion and Ethics broadcasts.