YOU probably won't be surprised by the latest figures which show that food prices rose by 1.7% in February alone, taking the annual increase to a hefty 11.5%. Expensive food has become a feature of our 21st century predicament. The spiralling cost of everything from bread and butter to rice and sausages can be explained away by world shortages of cereals (much of which is used as animal feed) caused by drought and flood brought on by global warming, as well as a booming world population. But it can't account for the enigma of UK vegetables prices, which have shot up mysteriously by 19% in just one year. I say mysteriously, because there is no reason for your spuds or carrots to go up more than any other category of food. True, last summer was a wet one, but this is nothing new in rainy Britain. So what's really happening?

The pricey veg mystery was elucidated most convincingly recently by a particularly articulate vegetable grower on Radio 4's Farming Today. The figures he reeled off were scandalous, offering more evidence of how supermarkets are crushing Britain's farmers and growers and leaving us recklessly dependent on imports.

Jeffrey Philpott gave the example of cauliflower, although his computation is doubtless typical of supermarket profit margins on other vegetables. It costs him 44p to grow a cauliflower, yet the supermarkets will pay no more than 36p a piece, even though they sell them for a cool £1.19 or thereabouts. Giving supermarkets the benefit of the doubt, each cauliflower may cost them another 14p in distribution and packing costs. Still, the arithmetic of cauliflower pricing exposes the venality of our large food retailers.

There they are, blitzing our TV screens with adverts for "inflation-busting" offers then putting a shameless, near 150% mark-up on exactly the sort of healthy, home-produced vegetable that public health campaigns exhort us to eat.

Last autumn, the National Farmers' Union warned that UK-grown cauliflower and other brassicas could vanish from plates unless farmers were paid a fairer price. If only this scenario could be dismissed as the perennial farmers' alarmism, but it can't and must be taken seriously. Supermarket profiteering is driving our native horticulture out of business. In the last 10 years there's been a 24% drop in the amount of land used to grow fresh vegetables in the UK. Our production is down 14% and imports have risen by more than a quarter. Why? Unable to sustain year after year of selling below the cost of production, farmers are diversifying into anything else as fast as they can. Great. Just when the world is running low on food and every sensible country should be building up its future self-sufficiency, our growers are giving up the ghost. Last year it was a shortage of caulis, this year already we are having to import carrots from as far away as Australia because we haven't enough of our own.

Price-aware shoppers have long recognised that supermarkets are expensive places to shop for fruit and vegetables. Anyone who uses an independent greengrocer, farm shop or even farmers' market stall can expect to slash their fruit and veg bill by a good 40%. But when most people felt flush, they didn't baulk at paying £2 for four overpriced apples in a shrink-wrapped pack. We haven't had a clue about what the going market rate for Canary cherry tomatoes or South African grapes might be, so fruit and vegetables have given supermarkets a licence to print money. But in the current economic climate, this profiteering has one very tangible result: people eat less. Last year, fruit and vegetable sales went down by a knee-jerk 12% when prices first began to soar, demonstrating the direct relationship between price and consumption.

Since 2001, the Department of Health alone has spent more than £6 million pushing its five-a-day health promotion message (the minimum intake to ensure wellbeing), and that's before you calculate the cost of similar initiatives in Scotland. It might as well have saved its breath. The last review of the Scottish Diet Action Plan, which prioritised this message, found that in a decade, there had been no increase in consumption; in fact vegetable consumption had dropped, so you'll be lucky if most Scots eat three a day. It's a miracle that we're not all coming down with scurvy and rickets. It's not just the nation's health we should be worried about. As concerns about the world's ability to feed itself mount, bodies such as the United Nations are urging us to eat less meat and eat more home-produced plant food. But the supermarkets are ruthlessly subverting these messages with their rapacious mark-ups.

We need a Scottish government inquiry into fruit and vegetable prices, but don't hang around for that. Ditch the supermarket, cherish the independent greengrocer, farm shop or market stall, and if you can, grow your own.

Supermarkets are depressing the uptake of fruit and vegetables through their greed and endangering our future food security along with it. They must be stopped.