The consumer champion carries out a monthly survey, tracking the average prices for a trolley of 19 items. These trolleys combine own-brand items like apples, eggs and tomatoes with branded goods like Hovis wholemeal bread. Prices are checked every day, to provide an average price for the trolley over the month.

Here is how the supermarket pricing broke down:

As you can see, there is a significant difference based on where you shop, with those picking up their groceries at upmarket Waitrose having to pay an average £8 more per week than those heading to the likes of Lidl and Aldi.

According to Which?, items with some of the biggest price differences included a popular tea brand, which is £1.51 more expensive at Waitrose than at Lidl. The price difference on own-label large free-range eggs is also stark, with some shoppers paying an extra £1.15.

Bigger shopping lists

Which? also tracks the prices of a larger shopping trolley, containing an additional 66 items, which includes a greater range of branded items. These include things like Branston baked beans and Kleenex tissues.

Aldi and Lidl aren’t included in this particular breakdown as they aren’t always available at the deep discounter supermarkets.

Here is how the main supermarkets compare on this larger trolley:

Asda is significantly cheaper than its rivals here, with shoppers paying around £18 less than those heading to Waitrose.

Which? pointed out that Asda has been the cheapest mainstream supermarket for more than a year now, dating back to January 2020, while it’s also notable just how close Sainsbury’s, Morrisons and Tesco are, with just £4 separating them.

Taking on the deep discounters

It’s clear that the bigger supermarkets are wising up to the challenge presented by the likes of Aldi and Lidl, and are now trying to rival them on price.

Last month Sainsbury’s announced a price-matching scheme with Aldi, promising to match the prices on around 200 items. It follows Tesco launching its own Aldi price match last year.