For the first time in a year I am contemplating making a trip to Tesco. In fact, while I am there I might well bung in my trolley my first ever bag of McCain oven chips.

Much as I have come to dislike the store, there is something I dislike even more: US presidential candidate Barack Obama singling out a British chain store in order to try to appeal to US workers.

Last week Mr Obama wrote to Sir Terry Leahy, chief executive of Tesco, protesting at the supermarket's refusal to recognise trade unions. He wrote, menacingly: “It is in your interest to ensure that the communities where you do business and the leaders of the workers in the industry are heard and that their concerns are heard and respected.”

To be fair, this isn't the first time that Barack Obama has made an issue of trade union rights, but why pick on a British company that, under the brand name Fresh & Easy, operates only 60 stores in one US state, California? Why not focus his energies on McDonalds, which similarly declines to recognise unions and which has a vastly greater presence on Main Street? Or why doesn't he repeat the attack he made on Wal-Mart two years ago, when he was a mere senator?

The answer, of course, is that a presidential candidate seeking the approval of swing voters doesn't go around attacking US icons. In fact, earlier this month Senator Obama made it up with Wal-Mart by appointing as his director of economic policy Jason Furman, an economist who in 2005 published a pamphlet entitled Wal-Mart: a progressive success story, arguing that cheap food helped the poor. Instead, Mr Obama has turned his guns on the - relatively - small target of Tesco, which allows him to appeal to the unions without appearing to be unpatriotic.

I am no friend of Tesco. A year ago I had a road-to-Damascus - or rather road-to-Newmarket - conversion. I caught sight of Tesco's ghastly logo, saw its horrid little plastic bags billowing from nearby trees and drove on to Waitrose instead. I can't stand the way that Tesco plays the planning system to its advantage. I detest the way it has used lawyers to silence critics of its expansion in Thailand - if Tesco is convinced it is a force for good in Thailand, why can't its PR department handle the case?

But then neither do I care much for protectionism, which has been a large feature of the Obama campaign. What his attack on Tesco really amounts to is: clear off, Brits - supplying cheap, quality food to Americans is a job for US companies. Either he should write open letters to the many large US companies that won't recognise trade unions or he should keep quiet on the subject.

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