Shoppers advised to check prices

An investigation by the consumer group found the schemes run by Asda, Sainsbury’s and Tesco differ greatly, making them of little real worth to shoppers.

Secret shoppers visited the supermarkets to find that, in most cases, each claimed to be cheaper than its rivals.

Which? analysed the till receipts from 19 Asdas, 20 Tescos and 20 Sainsbury’s outlets, checking the cost of each basket with the supermarket’s own online price match.

Asda was most often cheapest according to its “price guarantee”, Sainsbury’s was cheaper than Asda and Tesco for 10 of the visits and joint cheapest for another two, according to its “brand match”, and Tesco was cheaper than Asda and Sainsbury’s for 10 of the 20 visits according to its “price promise”.

Which? also found that just 30 er cent of shoppers trust supermarkets to charge a fair price for food.

Almost three-quarters of those polled (71 per cent) said price was one of the most important factors when shopping for food, suggesting that price match schemes can be an attractive incentive.

However, the 59 trips analysed by Which? produced average discount vouchers of just £1.45.

Which? director Richard Lloyd said: “Supermarket price-matching schemes can save you money but we believe they should be taken with a pinch of salt because they are difficult to compare.

“At a time when consumers are facing a squeeze on their household incomes, we want all the supermarkets to do whatever they can to help consumers find the best deal.”