In total, the basket of 42 groceries would have averaged around £11 more at Sainsbury’s Local and £10 more at Tesco Express for loyalty scheme members, compared to their price

Morrisons says it will roll out its discount More Card loyalty scheme to its convenience stores “in the coming months” after the Yorkshire company was criticised for higher prices in its smaller shops compared to its supermarkets.

An investigation has found that Tesco, Morrisons and Sainsbury's all charged more for a basket of shopping in their smaller local convenience stores.

The biggest different was at Morrisons Daily, where shoppers paid 21 per cent more on average. Which? found that Sainsbury's and Tesco had less variation in prices, but Nectar members could still be paying an average of 14 per cent more at Sainsbury's Local.

Morrisons Daily, Sainsbury’s Local and Tesco Express against prices at their full-sized supermarkets on three occasions in June and July, also checking loyalty scheme discounts. It found the biggest price difference for the basket was at Morrisons Daily,