Mr Cameron called himself a “convinced free-marketeer”, which means, with PC subtitles, that: “I am in favour of markets that work.” In this context, “work” means something other than supply and demand curves intersecting. It involves Britain having “the capacity to produce a significant percentage of its food”, hailing the rise of the “ethical consumer”, cheering on “food patriotism”, endorsing campaigns in favour of local food, standing up more effectively for those who produce such items and recognising that, in the Tory leader’s words: “All of us as consumers have our responsibility to try to buy quality produce from British producers, including local producers”. Government should be setting an example by securing “food for schools, hospitals and other public institutions locally”.

Mr Cameron has obviously identified a certain sort of upper-middle-class food mood and moved deftly to associate himself with it. By comparison, Mr Miliband, who referred to the need to encourage innovation to build market share and so justify continued public spending on agriculture, sounded virtually Thatcherite. The political message is that “local” has become the new “organic” in some quarters, with much earnest talk about the need to minimise the number of “food miles” accumulated. But is this really “food patriotism” or, essentially, “food protectionism”? And are the many environmental claims made on behalf of this influential lobby as impressive as claimed?

At a minimum, these matters are far more complicated than it was suggested yesterday. Organic farming, for example, demands a far larger area of land if it is to produce anything like the yield that modern agricultural techniques realise. This has an adverse environmental impact. Nor is the alleged advantage in health terms a settled fact either. As Peter Kendall, president of the National Farmers’ Union, has rightly said, the “high priests” of the organic movement should not be allowed to “demonise conventional farming.”

The question of “food miles” is not straight- forward either. Food that involves a large number of short local trips is not necessarily more environmentally friendly than that carried in a small number of long voyages. A study for ministers suggested that it would be better to drive in tomatoes from Spain during winter than grow them in heated greenhouses in Britain. Nor does environmentalism have a unique claim to virtue. What is ethical about protecting (overtly or covertly) EU farmers while denying impoverished producers in the Third World the chance to sell their fruit and vegetables in this country?

Mr Cameron appears to embrace an approach in which the normal laws of market economics are suspended in favour of rustic romanticism. The British have, though, benefited from comparatively cheap food in recent years because they have acted rationally and internationally about where food comes from. An increasing number of people can afford to be less picky about price and more selective in their purchases. But to be price-conscious is not to be unethical in an age in which many companies are striving to be ethical, a state that is not a given for politicians.

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