MOANING about supermarkets has taken over from expensive house prices as the favourite topic of conversation at trendy British dinner parties. To those for whom the choices of ordinary people are vulgar in the extreme, supermarkets and their cheap, varied goods have come to embody everything the bien pensants hate about modern capitalism. Hence the constant complaints that supermarkets are too successful; that they are attracting too many customers away from smaller, more expensive independent shops; and that they are squeezing their suppliers too much.

The British Left has always been hostile to big business and ignorant of economics. But Tory leaders should know better. Not David Cameron: he has jumped on to the anti-supermarket bandwagon as part of his mission to remake his party’s image, which now apparently means ditching his party’s traditional attachment to consumer sovereignty. Thus do the wealthy political elites of the metropolitan Right and Left make common cause against plain folk.

It is simply wrong for those rich enough to afford the expensive prices of small, independent stores and boutiques to seek to impose their lifestyle and spending choices on those who cannot afford them. Supermarkets have been one of the great forces for poverty reduction in modern times: they have done more to help struggling students and poor immigrant workers than any of Chancellor Gordon Brown’s incomprehensible tax credits or patronising handouts. The poor can now clothe and feed themselves for a few pounds in Tesco and Wal-Mart. Yet those who shout most about helping the poor are also loudest in attacking the supermarkets.

Competition rightly remains intense in the British retail sector, which is why prices are falling in real terms. Around 93% of customers have access to three or more retailers within a 15 minute drive; 98% of the population has access to at least one online grocery retailer. More and more goods are available: at last count, around 41,500 lines were stocked by the four largest supermarkets, an increase of 40% over five years. Despite its increased share of the retail market, Tesco makes only 3p in profit for every pound spent in its shops, thanks to fierce competition. Most of the huge productivity gains it and other retailers have squeezed out of the international supply chain have been passed on to consumers.

Since 1987, the price of clothes is down by about half in real terms and that of food by about a fifth; cheap imports from China would have led to lower prices even in the absence of supermarkets, but Tesco and its competitors have hugely magnified the effect. Given that the poor spend far more than Mr Cameron and wealthy left-wingers on clothes and food, they have gained the most: the majority of commonly purchased products are 10% cheaper in the four largest supermarkets than in other retailers.

The constant attacks on supermarkets are a reflection not just of economic ignorance at the highest political level but of Britain’s tall poppy syndrome. Tesco is one of the great success stories of modern British capitalism. Led by Sir Terry Leahy, the sort of gifted businessman in short supply in Britain, it has expanded all over the world. It is the biggest private sector employer in Britain and pays and trains its staff generously. This is not to say that Tesco is right about everything: its decision last week to cease supporting the campaign to liberalise Sunday trading is anti-choice and anti-growth. But most attacks on the company seem more inspired by jealousy and snobbery than by reason. They should cease – and politicians should grow up.