Eat your crusts. Clean your plate. With a wagging finger, the Prime Minister scolds the naughty nation for wasting food. In the latest Downing Street policy initiative we are back in the nursery, burying peas in lumpy mashed potato. We are reminded that children go to bed hungry in Africa (but no longer in China). Every year a British family throws away food worth £420, lectures Nanny Brown.

In the Cabinet Office, a team of researchers has concluded that at least a third of the food on our plates ends up in the bin. With an angry rustle of starched linen, the Cabinet Office announces war against food waste. “Most of this could have been eaten,” it concludes, primly.

Fresh from his barn-storming effort to get the world to produce more oil, the Prime Minister told G8 summit over the weekend that he wanted to help the world produce more food and reduce demand for food. Britain should play its part by “doing more to cut our food waste”.

We are irrelevant in all this. The escalating cost of food has little to do with our self-indulgence and a lot to do with the beginnings of indulgence elsewhere. Asians are enjoying eating more because they can now afford to do so. Population growth is part of it. We shall have to feed two billion more mouths by 2030 but it is the affluence of those mouths that is the challenge.

Britons noticed the surge in milk and cheese prices last year, caused in part by floods in Europe and drought in Australia, but that was just a trigger. The underlying cause was a gradual but accelerating shift in the Asian diet from mainly vegetarian to increasing consumption of animal protein. More Asian milk shakes, cakes and cheeseburgers led to a surge in the price of milk powder from $2,000 per tonne to $4,800.

Mountains of surplus EU grain and milk powder have shrunk, shipped eastwards. The International Rice Research Insitute says there is a crisis brewing in rice supply. Half of the world depends on rice to live but stocks fell earlier this year to their lowest level since the 1970s when Bangladesh suffered its terrible famine. The problem is not caused by the importation of Basmati rice to Britain; Basmati is in short supply - Asian supermarkets in Britain were rationing customers last month - but it is also a luxury product that most Bangladeshis cannot afford.

The problem lies with the lack of investment in new rice varieties, hybrids and genetically modified rice that might resist drought. It is the pressure on land in Asia from urban sprawl and the flight of farm workers to Asian factories.

The transition from food surpluses to food equilibrium and flirtation with shortage is causing panic. Nations are hoarding, Russia and Kazakhstan have curbed or banned grain exports and Argentina is taxing soybean that leaves the country. When trade is frustrated, shortages will surely follow.

So the eating habits of the British have nothing to do with rising food prices but a lot to with the need for land reform in the developing world, water supplies, access to markets and credit. It is also about better technology, including the use of GM crops that can resist pestilence and survive with little water.

The Prime Minister is obsessed with the notion that everything is connected. In the jargon of his policy unit, it implies a “joined-up approach to food policy”. It is true that energy and food are linked. Without a lot of the former - diesel for tractors and petrochemical-based fertilisers - there won't be much food on the table. But Mr Brown goes further, seeing a moral nexus between the half-eaten burgers that litter our streets and the rising price of wheat and meat across the globe.

It's the wrong way to look at the problem. Food waste and overindulgence is a sign of new wealth. It is no accident that America is afflicted by so many diseases connected with overeating. It is because so many Americans are recent immigrants. If you have been poor or you fear poverty, an abundance of food is comforting and a symbol of your newly acquired wealth. We shouldn't blame the overweight office cleaner with a fast-food addiction any more than we should blame the skinny woman who nibbles at her posh lunch. Both are food wasters, but they are a sign that Britain is rich.

In a market economy, it is not the ration coupon that determines our consumption but our ability to pay for excess. And, up until recently, we were in a position to pay for excess. In 1984, the average British household devoted 16 per cent of their spending on food. That figure now stands at 9 per cent.

When times are good, when borrowing is cheap, we divert expenditure from things we might need in the future to stuff we want now. We drink and eat too much and dine in restaurants. Today the opposite is happening. Money is tight and we are receiving price signals - use the car less frequently, shop at discount stores, forgo the Friday night blow-out at the Tandoori.

It is the market mechanism, not exhortation, that will stamp out food waste. Let's hope it won't last, so we can soon go back to being profligate.

Carl Mortished is world business editor of The Times

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