An online price-tracking website that’s constantly monitoring price increases and decreases across seven major UK online supermarkets can now reveal that Asda has again retained its title as the least expensive option for British consumers looking to keep their grocery costs down.

The results have been determined by carefully tracking how each online retailer prices the 42 items outlined in the Government’s Consumer Price Index ‘shopping basket’ on a week-by-week basis by the team at The latest research found that Asda is still the reigning champion – once again found to be the most affordable supermarket for shoppers throughout the month of May, with Sainsbury’s coming in second, beating both Iceland and Morrisons, with an average basket cost of just £113.68, compared to Asda’s £110.02..

Looking into price changes across the board, cheese at Morrisons was £2.50 in weeks one and two, but in week three shot up to £3.50, before dropping in price back to £2.50 for week four. Cheese at Sainsbury’s stayed at £3.50 for weeks one, two and three, then dropped to £2.50 in week four.

However, flour in Morrisons was £1.50 in week one and then dropped by 20p, remaining at £1.30 for the rest of the month. Flour at Waitrose remained at £1.50 for three weeks, then increased in price by 5p for week four.

Looking at Asda, the price of butter at the beginning of the month was £1.25 during weeks one and two, then increased in price to £1.80 for the last two weeks of May. Meanwhile, butter at Morrisons started at £1.87 in week one and then dropped to £1.25 for the remaining weeks of the month.

The research from May highlights that price changes are most common in week three for Asda.

Andy Barr, co-founder of, said:

“Despite Asda increasing its prices a fair amount from last month, it has once again retained its title as cheapest supermarket. It is interesting to see that Sainsbury’s are now coming in second after being in fifth place last month. For the last few months, they have been towards the more expensive side of the table, but recent price drops have now boosted them to second cheapest. Other superstores, like Ocado and Waitrose, are realising they need to up their game with major price drops compared last month, but at the moment both still remain as the most expensive supermarkets.” 

The online price-tracking website has been tracking the prices of 42 everyday items from the shopping basket on the Office for National Statistics’ Consumer Price Index (CPI) since 2019. Included within the list are items such as eggs, milk and bread, as well as non-perishables such as pasta, rice and cereal. The prices across seven of the largest supermarkets are analysed, with discount retailers Lidl and Aldi not included due to the inability for customers to shop full ranges online and not having the same like-for-like branded products that other supermarkets stock.

Own-brand items (or their equivalent) were monitored in the research to give the most unbiased comparison of goods and their prices, with the exception of branded items that all seven supermarkets stocked (e.g., Coca-Cola, Kellogg’s Cornflakes, etc.).

The full breakdown of each supermarket’s average basket costs, from lowest to highest over the four-week period in May, were as follows:

  1. ASDA – £110.02 (+£6.28 more than last month)
  2. Sainsburys – £113.68 (-£2.38 less than last month)
  3. Tesco – £114.75 (-63p less than last month)
  4. Iceland – £117.01 (+£1.14 more than last month)
  5. Morrisons – £117.06 (-£1.07 less than last month)
  6. Ocado – £124.07 (-£3.63 less than last month)
  7. Waitrose – £132.28 (+£4.74 more than last month)

To ensure the results across the stores are fair, if an item is unavailable or out of stock in one of the seven online stores for a whole week, then the product is dismissed and not analysed within the final basket costs for the month. Items can also be replaced with another like-for-like item, as long as it is in stock across all seven retailers. However, for the month of May, no products that were being tracked had to be swapped or were out of stock.

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