In the dog-end of the Christmas holidays my sons and a friend were re-creating the rolling boulder sequence in Raiders of the Lost Ark by charging up and downstairs pursued by my new purple gym ball. As the crashing reached a climax and Harrison Ford slammed his head into the bannister, I found myself thinking: oh, why can't they just sit down nicely and watch TV for a bit?

I soon stamped on this heresy, of course, since children doing vaguely energetic, imaginative things must be celebrated, at whatever cost to the nerves.

These days the mother who parks her kids before the Dave channel in order to work is no better than the one who shoves chips through the school railings to her children or feeds the family dog two-quid unhappy chicken just to hack off Jamie Oliver. A study this week by Childwise, a market research company, claims that four in five children have televisions in their bedrooms: that means 80 per cent of Britain is now officially common.

It's a class thing, children and TV: there is kudos in abstention, a snobbery in not living in one of those frightful working-class homes where the telly blares away in the background. “I'm really awful,” one mother told me with a smile that suggested she thought herself rather wonderful. “I only allow half an hour in the week and maybe an hour at weekends...after homework and clarinet practice.”

But in our multiplatform, interactive digital domain it's not enough to pull the plug out after Newsround. “Screen time” is the new playground buzzword. What irony that having wasted weeks acquiring the world's last Wii, and credit card bills still bulging from new PCs and plasma TVs, we spend the rest of the year fighting to stop our children using them.

Five hours and twenty minutes a day: that's the average media usage of a British child, according to Childwise. And maternal wheezes to bring this figure down are as variable and idiosyncratic as rival rail companies' pricing strategies. I know parents who have a rota pinned up to dictate whose day it is to play Guitar Hero, the music videogame. Others set egg-timers or print out ration coupons entitling the bearer to 30 minutes of Club Penguin, the virtual world. Like Madonna, some ban telly but permit movies. Not her own I hope.

I don't have the resolve for all this. Just every so often, when I'm sick of their sallow, supine bodies and the way the smaller one clutches the backless remote controls like holy amulets - even taking them with him to the loo in case his brother seizes power - I switch off their favoured doom-porn, Air Crash Investigation or Anatomy of a Grizzly Attack, and try to boot them outside. Only to see them graze idly at the computer instead.

It is no small challenge being the in-house Ofcom, diligently monitoring screen minutes: adding a half hour of MSN to Doctor Who and 20 minutes on SuperMario Galaxy. Does squinting at music videos on your iPod nano's teeny screen count? What about Tetris on your mobile? Is a podcast cause for concern?

Yet what exactly are we worried about here? Of course, the “toxic childhood” Jeremiahs are always plucking random figures from the air: Aric Sigman, of the British Psychological Society, declared that the Government should prescribe telly guidelines - two hours for seven to twelve-year-olds - just as it issues, say, a recommended sodium intake. Last year the University of California gave warning that between two to four hours of TV watching risks high blood pressure. Other reports claim that more than four hours a day leads to obesity, attention deficit disorders, linguistic problems and even back pain. They may as well add, like parents did in the Seventies, that sitting too close to the box gives you square eyes.

Screen-time policing is the nexus between our fears for our children and our anxiety about the future. Technology boggles us with its unfathomable black magic: what if Microsoft used its power for evil and patented spyware that could suck our brains out through our noses? But our children with their instinctive understanding of new systems, stroll with happy confidence through the techno garden.

We feel warm inside when they play retro boardgames of wood and paper just as we did. But the computer is the ultimate plaything, indeed almost precludes the need for any other toy. My sons' joint Christmas present last year was the most basic AppleMac. Whereas I use my computer as little more than a typewriter that can order groceries, they have figured out how to record music, edit photos, play chess, make stupid webcam films of themselves pretending to be Ant'n'Dec, download embarrassing (to their parents) rock like Metallica, print jam-jar labels, correspond with a godmother in Australia and do stop-start animation with Plasticine men. I was reminded of how, at a similar age, my friends and I tried to record a panto on my parents' reel-to-reel tape machine. The spools got all twisted. It was rubbish.

As for TV watching, it is reassuring to learn that, according to Childwise, The Simpsons is our children's favourite show. “Television!” sighs Homer. “Teacher, mother, secret lover.” How can you object to your children being schooled in subversion, post-modernism, American politics, film pastiche and a hatred of clowns?

But I know several families, the loveable flat Earth, Amish folk, who refuse to have a TV at all. One has a black-and-white on which the husband is permitted to watch Arsenal games in the shed. Their children come round, see three old episodes of Top Gear stacked up on our SkyPlus box and to my sons' frustration refuse to do anything but sit drooling until dragged home.

Once, such kids would be the playground outcasts, but no longer. Mine are. Because, unlike the TV-hating parents, I refuse to buy them portable gaming consoles, Xboxes, GameCubes, PS2s. These are Satan's Sudoku, crack cocaine of the brain. Even the crappiest cartoon or lamest soap teaches a child about character, plot, drama, humour, life. Playing videogames, children are mentally imprisoned, wired into their evil creators' brains. And they play them - beepety-beep - on journeys, over family meals, any minute in which they find themselves unamused.

And their parents never seem to say, hey, this is the bit where you pick up a book. Or game over, kids: get an inner life.

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