The consumer champion compared prices for a basket of 23 items throughout last month and found that, on average, shoppers would have paid £24.24 at Aldi, beating rival budget supermarket Lidl by just 73p.

The most expensive supermarket – Waitrose – was more than £9 more expensive than Aldi for an equivalent basket of groceries.

To compare prices, every day in October Which? checked the prices of 23 items, including own-brand products such as apples and eggs as well as branded goods such as Hovis wholemeal bread, to see how the UK’s supermarket chains compared.

Aldi came out cheapest overall, at just £24.24, while Lidl was £24.97. Asda was the cheapest ‘big four’ supermarket, with the basket costing £25.94.

Waitrose was the most expensive at £33.81 – equating to 39% more than Aldi. Groceries with some of the biggest price differences included own-label seedless grapes and own-label melon, both of which had a difference of £1.11 between Aldi and Waitrose, and PG Tips tea bags, which had a difference of 94p.

Which? also compared a bigger shopping list of 77 items. This included a greater selection of branded items, such as Cathedral City cheddar and Colgate toothpaste, that aren’t always available in the discounter supermarkets, so the bigger trolley comparison didn’t include Aldi or Lidl.

For the longer list, Asda, at £143.21, was the cheapest of the traditional supermarkets, with Sainsbury’s slightly more at £145.56. The same shopping at Waitrose cost £164.91.

Julie Ashfield, managing director of buying at Aldi, said: “We’re dedicated to providing our customers with the best prices possible for the highest quality products. With Christmas just around the corner, we’re proud that we’ve been yet again recognised as the UK’s cheapest supermarket.”