In the past year, I have become quite familiar with a radio station that broadcasts along the south coast. Wave FM plays a relentless stream of upbeat pop from the 1980s and 1990s - just the job for leavening the journey to and from lectures about global pensions systems. There is thankfully little talk on Wave FM, but what there is consists of adverts. And that means government adverts. You don't realise until you leave London quite how many of these there are. They dominate local radio.

And what adverts! Relentlessly plumbing the depths of human misery, they project a vision of British life that is entirely negative. If they are not patronising you, they are trying to terrify. It doesn't help that, interspersed as they are on Wave FM with happy, poppy stuff, the advertising jars so badly. You've been trilling along to "Club Tropicana", South Downs flashing by, lambs skipping in sunny fields, when your thoughts are interrupted by a voice, heavy with threat: "Your internal organs will keep travelling until they hit your ribcage . . ."

Tick tock

Cars crash. Children die (cue, cute-sounding kid: "Ooh, what's this place? Why is that car all crushed?"). Parents separate and mums worry about child maintenance. People slip and trip at work because somebody didn't mop up; bosses don't pay the minimum wage. Dads become unhealthy and forget to have their midlife check-up. We talk on our mobile phones while driving, or nick benefits, or report those who nick benefits, or watch TV without a licence, or stop on level crossings. So idiotic are we that it's amazing any of us is alive and sentient - presumably due entirely to the interventions of the government.

My current favourite is the online paedophiles advert. A clock ticks. Sounds of children playing. "It's nice to hear children having fun." Then the sounds stop, except for the menacing, slow ticking of the clock. Maternal voice: "It's when it goes silent that you begin to worry . . ." (This may not be exactly accurate because if I'd tried to write it down while I was driving, there would probably have had to be a safety campaign about that, too.)

Sometimes, you get three of these in a row: I once heard advice about wasting less food, followed by "You're entitled to the minimum wage", then a warning not to leave valuables on display in the car. About three-quarters of the ads on Wave FM are public advertising, I reckon. It's rarely less than half of any ad break. And they are relentlessly, often hilariously, depressing. Voices are either threatening or sorrowful. The only upbeat one I heard was in the run-up to the general election, when, with great relish, a "bloke-next-door" voice urged listeners to suggest suitable punishments for local offenders doing Community Payback. It all amounts to a stunningly negative vision of Britain that is going to make people feel bad either about their country, or bad about their government for trying to make them feel bad about it.

But now, the adverts, with the exception of the one about paedophiles, have stopped. This may be because of the World Cup - the ads were replaced with private slots trying to sell stuff like pizza off the back of the football. Or it might be because of the change in government. If so, the impact has been swift and I fear for the future of local commercial radio.

While the Lib-Cons' pledge to cut 25 per cent of all departmental budgets is either absurd and deceitful or absolutely terrifying, it is hard to argue against their promised cuts in areas such as marketing and advertising, in the face of such relentless rubbish. The Lib-Cons (or "the government where the Libs get conned") have promised to halve the £540m-a-year advertising budget. Few will weep for the loss of the "slips and trips at work" ad, or mourn the end of the reminder about their check-up.

Shock and awe

Unfortunately, it is the more shocking advertising that has been shown to work. People do not respond to kind admonition as they do to a picture of a diseased lung. But the precise effects are difficult to quantify. A paper produced by the Health Development Agency a few years ago reported that a television advert reduced smoking by 1.2 per cent over 18 months. It didn't say how much it cost to produce and broadcast the ad, or for how long people stopped smoking. The Active for Life campaign in the 1990s, which encouraged people to exercise five times a week for 30 minutes, increased knowledge of the campaign but had no impact on the amount of physical activity of Britons.

People might watch the ads, but that doesn't mean they are going to get off the sofa as they crack open another beer. Healthy-living advertisements are also known to have least impact on the people to whom they are targeted. Those who already eat healthily might have another apple a day because they saw the "five fruit and veg a day" ad, but those with unhealthy diets will just reach for another bag of crisps and the remote control.

Most serious studies today report similar findings about public health campaigns. An element of shock and a simple, targeted message, together with an easily manageable recommendation - an alternative behaviour rather than an order just to stop - have the most impact. The Child Exploitation and Online Protection Centre advert about the dangers of online paedophilia will probably prove effective: it is alarming, clear and offers a simple solution (Internet Explorer 8, in case you're wondering: ceop.gov.uk/ie8). On the other hand, the impact is minimised if the ad is sandwiched between the plaintive voice of a dead child and the sound of an organ hitting a ribcage, at which point all of them become funny. It is possible to become saturated with horror stories. Sometimes - as all those health campaigns are essentially trying to tell us - less is more.