Many independent sandwich shops and cafés would go out of business if they were obliged to serve food that was healthy, fair, and green, according to a damning new report from the New Economics Foundation (NEF).

An Inconvenient Sandwich: the Throwaway Economics of Takeaway Food criticises small outlets for selling "clone food" supplied by wholesalers, which is "heavily processed, globally sourced, and mass-produced".

NEF said they knew little about where the food came from and did not think their customers cared. Caught between cost constraints, customers’ demands for certain foods and their inability to specify beyond the suppliers’ inventories, they did not feel they had much control over the range or provenance of the food.

However, the report was sympathetic to these outlets, adding: "Taking steps to improve environmental or social sustainability, for example, by raising the quality of the food, is likely to increase costs to such an extent that economic sustainability is threatened. This is because we are accustomed to paying an unrealistically low financial price for our food."

Jim Winship, director of the British Sandwich Association, said it was misleading to lump together sandwich bars, cafés, pizza operations, fish and chip shops and burger bars, as their customer profiles, products, ingredients and distribution channels were all quite different.

He said: "Many businesses we deal with are committed to buying locally and supporting sustainability across their supply chains. Most customers buying lunchtime sandwiches demand quality and the research we do suggests they are prepared to pay for this provided they feel they are receiving value for money."