Yes, I too was one of those told as a child to "think of the starving people in India" and eat up all the food left on my plate. Any retort on my part, such as that the starving people in India were welcome to it, was not always appreciated.

Partly for this reason, I haven't tried a similar form of moral blackmail with my own children; and besides, there are no longer any famines in India, which is now a net exporter of food. On the other hand, it is undeniably the traditional duty of parents to explain to their children why they should finish the food on their plate – even if we privately concede to each other that this is a waste of time as well as food.

Now, help is at hand, and from an unlikely quarter: into this domestic moral minefield steps our Prime Minister. On the plane out to the G8 Summit in Hokkaido, Japan, Gordon Brown told the political lobby journalists accompanying him: "If we are to get food prices down, we must do more to deal with unnecessary demand, such as by all of us doing more to cut our food waste, which is costing the average household around £8 a week."

To judge from the reaction when the BBC put these words on its internet noticeboard and asked for comments, Mr Brown's suggestion has not gone down too well. Typical of many who clearly felt that that they were indeed being treated like children, was this response: "Go away, leave me ALONE; if I choose not to eat my greens, it's none of your business."

Perhaps Gordon Brown did not say that, exactly: but since the relevant Government-sponsored report argues that "the main reason for throwing away food that could have been eaten if it had been managed better" is the stuff "left on the plate after a meal", it's not such an unreasonable response.

It's true that there are other, lesser, reasons for food waste; most notably that a large amount is thrown away uncooked and even unwrapped. Here, the nanny state is itself a part of the cause of the waste: 12 years ago (under a Conservative Government) labelling regulations were introduced, which demanded that all food products had to be stamped with an "appropriate durability indicator".

Ever since, nervous consumers have felt oppressed by the tyranny of "best before" dates, throwing out food which is perfectly safe to eat – and would be for some days to come. You can blame the supermarkets if you like, for being unduly cautious with these "best before" dates, but given the mass hysteria which is nowadays whipped up by an outbreak of genuine food poisoning, their conservatism is hardly surprising.

There is, however, one cause of waste which is so obvious that the Government completely fails to mention it: food, by historical standards, is extraordinarily cheap. Fifty years ago, 30 per cent of the average British family budget went on food. Yet according to the report released yesterday by the Cabinet Office, entitled "Food Matters-Towards a Strategy for the 21st Century", "the average UK household now devotes around 9 per cent of its expenditure to food".

Even if these figures don't take account of the most recent spike in food prices, this represents a remarkable period of sustained real price deflation. Look again at the Prime Minister's statement: how much per week did he say that the average family loses, with all its wasted food piling up in the rubbish bins? Eight pounds. The figure is striking not for its significance, but for its marginality.

It is shatteringly obvious that the cheaper something becomes, the more likely we are to "waste" it – the same principle is seen in the clothing market: if a T-Shirt from China costs only £2.50 then the purchaser in Oxford Street will not feel bad about wearing the thing only once or twice before discarding it.

This principle works in reverse, however. Gordon Brown seems to think that the public need to be told that as food prices increase we should waste less of it. There can scarcely be a family in the country – and especially the poorest– to whom this thought has not occurred: they are being condescended to by the Prime Minister, from a cruising altitude of 30,000 feet.

This newspaper appears to have been given an additional briefing from the same source. Yesterday's Independent carried a story from its man on the Prime Ministerial flight underneath the headline, "Supermarkets will be told to stop offering bulk-buy deals". The report itself said that "supermarkets will be urged to drop 'three for two' deals on food that encourages shoppers into bulk-buying more than they need." The most criticised of these deals are known as "Bogof" – Buy one, get one free.

Isn't this truly extraordinary? at a time of sharply rising food prices, when the least well-off are desperately looking for bargains, and trying to make the housekeeping pound go that little bit further, Gordon Brown apparently intends to make it more difficult for them to find the offers which will feed their families most cheaply.

Perhaps it has also escaped the Prime Minister – despite his celebrated attention to detail-that the vast majority of "Bogof" deals in supermarkets are for goods which can be frozen. Yes, that's right: most families actually have things called freezers into which they place the "free" part of the Bogof package, to consume at a later date.

If anything, such "value" purchasing is likely to increase in the present economic circumstances. If you want the clearest possible illustration of the direction British shoppers are moving in, observe last week's dire figures from Marks and Spencer's very upmarket food business, while discount food stores such as Lidl are expanding.

It should also be obvious to anyone with a rudimentary understanding of economics that discounts are the way businesses attempt to bring supply and demand into balance – and thus reduce waste. If supermarkets have overbought a particular line of food – and it is impossible to be completely sure of how something will sell – then they will cut the price to shift it. The alternative is for more food to go straight from the shops into landfill.

The Liberal Democrat Environment spokesman, Steve Webb, accuses the supermarkets of easily avoidable overstocking – almost as if they wanted to lose money. Yet the people who actually run these highly competitive businesses spend almost every waking minute trying to reduce such inefficiencies.

As one supermarket employee told me yesterday, with more than a trace of exasperation: "We'll consider lessons from politicians on how to run our supply chains, in the same way that politicians would take lessons from us on how to deal with their constituents." Or, in other words: Bogof, Brown.

d.lawson@independent.co.uk