Shopping at a smaller store for convince could be costing you a fifth more compared to a larger supermarket, Which? has found. The consumer champion compared the cost of 42 grocery items at convenience chains Morrisons Daily, ­ Sainsbury's Local and Tesco Express against prices at their full-size supermarkets. 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. Tesco Clubcard holders could be charged 11 per cent more at Tesco Express despite them offering Clubcard prices. For example, a pack of six Mr Kipling Bakewell Slices was £2.

32 on average at Tesco Express but £1.50 at Tesco supermarkets - a 54 per cent difference. READ MORE: The scandalous truth about Birmingham's child poverty emergency laid bare A 500g bag of own-label fusilli was 31 per cent or 20p cheaper at a larger Sainsbury's supermarket at 65p instead of 85p.

A medium white Hovis loaf cost 12 per cent more at both Sainsbury's Local and Tesco Express, and 14 per cent more at Morrisons Daily. The 42 groceries averaged around £11 more at Sainsbury's Local and £10 more at Tesco Express for loyalty scheme members compared to their prices at the larger stores, adding up to more than £500 over a year. Two pints of own brand semi-skimmed milk cost eight per cent more at all three supermarket convenience stores.