It's almost a year since I first heard my Edinburgh neighbours (two cars, three foreign holidays a year, contemporary art collection) boast about the savings to be had at a hilariously spartan supermarket down in Leith. It was called Lidl. You knew then that Marks & Spencer's food business was in trouble. And its even posher rival, Waitrose, and, indeed, the organic farmers in their scrubbed-up wellies at the Saturday market under Edinburgh Castle.

The key force behind Britain's better food revolution - an extraordinary upheaval during which organic sales have risen by an average 26 per cent every year for 15 years - was not worry about health or the environment, but a middle-class willingness to pay more, sometimes a fantastic amount more, for their groceries.

It's over now, for a while at least: a party spoilt by the double dampener of rising world food prices and a slumping economy. That's less rational than you might imagine. But for the moment, such fripperies as chopped and washed vegetables at three times the price of doing it yourself (£2 for 400g), or Sprouted Pea and Bean Salad with Mint Dressing at £2.09 for 165g (about four mouthfuls) are decadences as passé as larks' tongues in aspic. This week M&S, which sells these fripperies and more, announced that it is closing 25 of its Simply Food outlets. The shops, many in railway stations, were aimed entirely at the affluent middle class in a hurry. Now those people are in a panic.

M&S's profits on food were down last summer - so much so that it sacked its head of food, Steven Esom, known for his success in flogging high-premium groceries to the better-off. He had done similar work at Waitrose. But even such a brilliant retailing innovator could not buck the demands of shareholders. The “big four” supermarkets' profits rose healthily through 2008, and upstart discount stores such as Lidl and Aldi recorded double digit sales increases. But M&S went the other way. Waitrose's profits also drooped.

The organic trade is also in trouble. Sales are down 20 per cent at Waitrose alone. Since the summer egg farmers have often had to sell organic eggs for the price of ordinary ones, and the same has happened with some meat, notably lamb. The organic-certifying organisations are considering asking the Government for permission to let farmers off some feed restrictions. Almost 50 per cent of consumers, according to a Mintel survey, are reducing spending on organic purchases or don't think they will be able to afford them again.

This would make sense if we were broke and struggling to feed our families. But we aren't. Not yet.

Instead, the British middle class is indulging another addle-brained craze - thrift chic. Just as my wealthy neighbour once hid Tesco bags - so vulgar - now she flaunts ones from even cheaper stores. We buy brisket and cancel restaurant reservations because it's cool to eat like granny did in the Second World War. This outbreak of pay-less fever is silly, and terribly damaging to producers and shops who have carefully built up the business of supplying better, more sustainably produced food. It is also particularly peculiar as it contradicts a host of other powerful consumer obsessions of our time.

We have not suddenly stopped worrying about the cleanliness of our food, or its contamination with additives. We still ache with nostalgia for the traditional farming landscape. We weep with the celebrity chefs over the treatment of pigs and chickens. Everyone says that they want a cleaner environment. And we worry about how fat we're all getting. But we want to pay less for our food.

The truth is that better food is more expensive food, and many of the ills in our present supply system could be tackled if we paid more for it. Organic fruit and veg don't just contain more nutrients and fewer artificial chemicals, they are grown by a system that uses 26 per cent less energy than conventional farming. If you want your bacon from a pig that spent a decent life eating natural food, you must pay about three times as much for it as for basic streaky from the Continent. The same goes for chicken. In animal farming, cheap is always the cruellest.

The closure of M&S convenience food shops is no great loss to the food-loving nation, But it is a real blow to the novel idea that food need not be sold primarily on “value”; that, with proper inducements, consumers will pay a little more for quality, lack of chemicals, animal welfare and to support local and traditional farming.

Waitrose, and to a lesser extent M&S, were doing good things to support these notions. They had begun to label properly, so you knew where food came from. They had made real commitments to cut waste and carbon emissions. Waitrose undertakes long contracts with farmers, and buys entire animals, thus taking on the burden of seeing that every bit of the carcass is used.

Pay more? In 2009? It's not an easy sell. But we spend very little in real terms, on food: less than anyone else in Western Europe. Even now only one pound in ten spent by a British household spends goes on food and drink. In 1970 we spent twice as much. In 1955 about a third of British household income went on food. The truth is that most of us can still afford to spend more on food: takeaway sales are booming. If we spend our money in the right places, in shops and restaurants that genuinely take care of producers, or directly from farmers, the good food revolution may not be over.

Alex Renton's Jack Sprat column is in times2 today

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