Environmental groups and independent retailers have poured scorn over Tesco’s local food claims. This week, Tesco reported a 40% year-on-year increase in sales of locally sourced food, and claimed to be on track to generate £500m in sales of local produce.

But Friends of the Earth warned that supermarket local offerings were not always as local as they seemed. “So-called ‘local’ supermarket produce is often trucked around the country before it reaches shelves,” said supermarket campaigner Helen Rimmer.

“And farmers and suppliers don’t reap the benefits, as supermarkets continue to squeeze them for ever-lower prices. Buying directly from farms, markets and independent stores is better for farmers, the local economy and the environment.”

Traditionally, food was defined as local if it came from within a 30-mile radius of a store. However, at Tesco local is now synonymous with regional and is defined by county, or in Scotland and Wales, by country. A Tesco spokeswoman said it had asked customers in different regions what local meant to them, and worked from that definition.

Independent retailers have been quick to point out the disadvantages of supplying the multiples. While the scale of supermarkets often rules out small suppliers, independents were happy to do business with them, said Jonathan James, who owns five independent stores in Cambridgeshire.

“Tesco can only deal with suppliers who can manage the volumes it sells,” he said. “I can deal with genuine cottage industries – suppliers who grow less in a year than a Tesco store would sell in a day.”