Shopping for food at convenience stores run by larger supermarkets could cost consumers up to £800 more each year, new research shows.

According to data from Which?, leading retailer Tesco was found to charge higher prices at its Express convenience stores than at its larger supermarkets.

The consumer watchdog found that purchasing 75 items at a Tesco Express would cost £15.73 more for an average weekly shop, rather than buying the same items online or at a larger store.

As a result, this could add up to £817.91 more over a year’s worth of food shops.

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The data also found that shopping for 69 items at a Sainsbury’s Local convenience store would add an extra £9.19 to a weekly grocery bill and £477.93 over a year.

The Big 4 grocer’s Local stores were found to be more expensive on items including Heinz Cream of Tomato soup with a 19% higher price tag than at a larger store.

At Tesco’s convenience outlets, sweet potatoes saw the biggest price difference at 37% more expensive, with a 28% difference for Mr Kipling Bakewell slices.

“Shopping at a supermarket convenience shop comes at a cost,” Which? head of food policy, Sue Davies said.

Sainsbury’s told the Mirror: “Our Local stores are in city or town centre locations and operating costs are higher.”

Tesco added :”We work hard to ensure our customers get great value online, in a large store or in an Express store.”

This comes as NationalWorld’s exclusive tracker of supermarket value range food, drink and cleaning products, found that grocery retailers are continuing to impose sharp price hikes on their budget food items as inflation starts to drop.