If we lived in a benign dictatorship (and I was the benign dictator), I'd ration television to two hours a week. Don't imagine I'm a paragon who spends her evenings listening to good music and perusing literary tomes. I turn on the news and gaze blank-eyed and slack-jawed at whatever follows, right up to bed time, more nights than I care to admit. But on those occasions where work or mechanical failure comes between me and the TV, have I missed it? No, not at all.

Television is a national addiction. It must be. Why else would it seem punitive to restrict watching it? We don't go to the cinema every day. We don't attend plays or concerts every day. We can keep up with the news on the radio or in news-papers. So why do so many people need to switch on their TV when they get in and leave it flickering and jabbering in the corner hour after hour? Watching it is a compulsion, yet if we accept the findings of Dr Aric Sigman, every responsible parent (and every ambitious one) should have a padlock on the "on" switch, partly for their own sakes but mostly for their children's.

He says television is linked to the development of Alzheimer's disease and to type-2 diabetes in adults. His research points to a link between watching television and clinical depression. It affects our metabolisms so that we use up to 211 fewer calories a day sitting in front of the soaps and doing nothing.

It's even worse for children. Just a few hours' viewing a day could be enough to make a child fat, dim, with attention deficit hyperactivity disorder and early onset of puberty. It can damage their learning ability permanently.

If anyone had told us when we were leaving the maternity ward with our precious progeny, that Blue Peter and a few cartoons could frazzle their brain cells, we'd have thrown the telly in the bin the minute we got home, wouldn't we? Or would we still have marvelled at what a brilliant baby-sitter the flickering screen was and said: "Well, it never did us any harm."

Yet Sigman says the developing brains of the under threes are particularly vulnerable to damage. Older children with a television in their bedrooms tend to be bottom of the class.

Sigman sounds like one of those old blokes who used to march around wearing a sandwich board that listed the multiple evils of eating red meat. The trouble is, his claims are not dreamed up. He is an associate fellow of the British Psychological Society and a member of the Institute of Biology who has worked his way through the available scientific research and brought together the findings.

He's even looked at changes in societies where television was introduced for the first time. In Bhutan and in Tonga it was swiftly followed by an unprecedented crime wave.

You have to ask yourself if Doctor Who and Desperate Housewives are really worth it.

He says that by the time we reach 75 we will have spent 121/2 years watching television. What a waste of precious time. But if you think that's bad, the average 11 and 12-year-old spends 53 hours a week on the computer or watching TV. That's longer than they sleep, or spend at school. What sort of a childhood is that? And what sort of parents does it make us?

It's the modern way, people say. But what is a modern childhood? Childhood is what adults decide it is. After all, babies don't arrive with fixed expectations. It only takes an act of will to give them the sort of childhood they deserve, the sort you hopefully had yourself.

I saw television for the first time when I was about seven and for the second time a year or so later. The rest of the time I was always out of doors. Say childhood to me and in my mind's eye I see twirling skipping ropes and hear the chant of Darkie Bluebells. I remember games of tig and dens made out of old bits of tarpaulin and broken tea chests with pine branches for carpet. I remember dressing-up, making-up plays and sitting on a swing in the twilight.

I also remember huffs and sulks and tears before bedtime. And home? Yes. Home was a place to run to for a jersey if it was cold or a coat if it rained. Bee stings were smeared in something blue and grazes wiped with antiseptic after which your mother would declare, "You'll live" and off you went out again until supper time.

It was a childhood that, far from damaging the brain or shattering the attention span, taught me much of what I know about people. There was a children's world, where you had to learn to read the intentions of others; to know when you would be welcomed and when shunned. It wasn't always gentle but it was imaginative, instructive and adventurous.

It held undoubted dangers. As a parent, I pale at the memory of my sister walking the high wall of an ancient viaduct, or the way we used to cross rivers on stepping stones or by balancing on an old sewage pipe when the flow was too fast. But it taught you about balance, about risk and about the exhilaration of survival.

The world is now a busier and more dangerous place. That level of parental relaxation is probably no longer possible, relying as it did on a close-knit community where every adult who saw you, knew you. But surely it isn't beyond the power of our imaginations to create arenas where children are able to play together in groups.

Instead of accommodating their needs we label today's youngsters a problem. We have CCTV cameras to spy on troublesome teenagers on bleak housing estates and Asbos or curfews to control them when they get out of order. When they move out of school and on to benefits we watch their younger brothers and sisters take their places.

Why can't we start looking at them, at all kids, as an opportunity? We could start by filling their surroundings with safe areas, staffed by youth leaders, where they can play and explore in safety.

We need to have a major re-think that puts children, instead of cars, at the centre of our town planning. There are parks but by and large they are dismal expanses of lawn with barely a tree to climb. There is the odd adventure playground and there is a smattering of sports centres. Meanwhile, all around us are cathedrals to shopping with heated malls and generous acres for supermarket car parking. Why aren't there safe play areas there, with bikes and balls and skateboards as available as shopping trolleys? Instead, children are trailed around the aisles, bored, whingeing and often earning a clip around the ear - or left at home watching telly.

The next time Tesco or Waitrose or Morrisons want a superstore, let's make a super, supervised staffed outdoor playground, open to the community, a condition.

We pay lip service to our children being the centre of our universe. We buy them designer clothes and expensive electronic equipment. Then we leave them to it. If they had the option of getting out with their friends to have adventures in a place they could call their own, they wouldn't be half so keen on their screens.

There are obvious benefits to television and computers. Of course there are. There are friendships to be built through chat rooms. There is information from wildlife programmes, the news and documentaries on TV. There is also enjoyable garbage.

But like the garbage we like to drink and like to eat, it needs to come with a health warning. We need to limit our consumption. In my benign dictatorship, television would be restricted - but with so many better options the children might even choose to give it a miss.