Shoppers who chose Aldi could save £17 on average when compared to the most expensive supermarket, Waitrose.

The cost of a basket of 39 popular items was £69.99 at Aldi and £87.33 on average at Waitrose. The second-cheapest supermarket was Lidl, where the basket would cost £70.64.

Aldi has consistently been the cheapest supermarket for the last 11 months and it has also announced a big expansion, hiring 6,000 new staff this year.

Asda is the cheapest of the big supermarkets

Which? also compared the cost of a larger basket, of 135 items, among the big supermarkets. This basket included some branded goods, including Cathedral City cheese and Andrex toilet paper, and the discount supermarkets were not included.

From this comparison, Asda was the cheapest supermarket with the basket costing an average of £343.46. It was 11% more expensive to buy the same basket of goods at Waitrose, the priciest supermarket on the list, where it would cost shoppers £382.22.

The second-cheapest was Sainsbury’s, where the basket would cost an average of £353.96. It was followed by Morrisons (£355.84), Tesco (£365.77), and Ocado (£374.53).

Which? is urging the supermarkets to do more to help shoppers with rising prices. Food inflation hit record high levels in April, up by 15.7% from March, according to the British Retail Consortium (BRC).

It is now growing at the fastest rate seen in 45 years with the price for basic goods, such as cheese and porridge, rising by 80%.

Supermarkets ‘not doing enough to help shoppers’

The consumer group said many of the major supermarkets have not done enough to help customers in the cost-of-living crisis and they should be making sure affordable basic ranges are available in all branches.

It comes as research from Which? showed that smaller convenience stores hardly ever stock the cheapest own-brand products.

Ele Clark, Which? retail editor, said: “The price of food and drink has continued to soar as people suffer through the worst cost of living crisis in decades. It’s no surprise to see many people turning to discounters like Aldi and Lidl when our research shows they could save up to £17 on a basket of everyday groceries by doing so.

“Supermarkets aren’t currently doing enough to help shoppers. Which? believes the big retailers have a responsibility to ensure everyone has easy access to basic, affordable food ranges at a store near them, and to provide transparent and comparable pricing so people can easily work out which products offer the best value.”

Julie Ashfield, managing director of buying at Aldi, said: “At Aldi we believe access to great quality food and drink is a right not a privilege. Shoppers want to know they are getting great quality produce at the best possible prices.

“So, to have Which? name us the UK’s cheapest supermarket for the eleventh month in a row is reassuring for our shoppers.”