Asda has beaten rivals Tesco, Morrisons, Sainsbury's, Waitrose and Ocado to the tile of cheapest online supermarket.
Online price-tracking website Alertr analysed week-on-week how each online retailer priced the 42 items in the government’s Consumer Price Index ‘shopping basket’.
Aldi and Lidl were left out of the price comparison as their full ranges are not available to buy online.
Fresh produce like eggs and milk, as well as bread, pasta, rice and cereal were included in the shopping basket along with own-brand items or their equivalent.
READ MORE: We tried 10 everyday items from Aldi and Asda to find out which is cheaper
Asda was found to be the most affordable supermarket once again with an average basket cost of £108.72.
Sainsbury’s came in second once again with an average basket cost of £113.34 while Tesco was in third place at £113.92.
Waitrose was the most expensive at £126.77.
The full breakdown of each supermarket’s average basket costs, from lowest to highest over the four-week period in September, were as follows:
1. ASDA – £108.72
2. Sainsburys – £113.34
3. Tesco – £113.92
4. Morrisons – £117.54
5. Ocado – £122.57
6. Waitrose – £126.77
Looking into price changes across the board, Morrisons started the month selling its cheese at £3.50 per block, and then for the remaining three weeks of September the price dropped by £1 to £2.50.
However, at Waitrose cheese was £3.50 for the first half of the month and then went down in price to £2.75 for the last half.
The price of gin and vodka fluctuated for Asda during the month, varying between £13 and £15.50. This cost bracket rang true for all six stores, except for Morrisons whose gin and vodka started the first half of the month at £13 before jumping up to £16 for the second half.
For the month of September, the cheapest supermarket for Prosecco was Waitrose at £6.99. However, it was the most expensive for Whole Milk at 90p, 10p dearer than at most of the other supermarkets analysed.
Looking at coffee specifically, Waitrose joined Asda, Tesco and Sainsburys selling the product at £4, then at week three increased steeply to end the month being the most expensive for coffee at £6.50. Meanwhile, Tesco remained the cheapest supermarket for Tea Bags throughout the month.
The research highlights that price changes are most common in the middle of the month for most of the stores analysed, with the average trend being that prices then start higher then decrease.
The biggest weekly increase in grocery prices was found at Asda, whose prices shot up by 6.3 per cent between the week commencing September 3 and week commencing September 10.
The biggest weekly decrease on the other hand occurred at Morrison’s, whose prices dropped by 4.4pc between the week commencing September 10 and the week commencing September 17.
Andy Barr, co-founder of www.alertr.co.uk, said: “It is interesting to see that the six supermarkets have stayed in a similar price order to previous months.
"There definitely seems to be similar price across the board, with a relatively large difference between the top and bottom spots on the leaderboard of £18.05.
"Dropping their prices, Sainsbury’s are becoming one to watch as they have stolen second place from Tesco, who was regularly second most cost-effective earlier in the year.
"Ocado and Waitrose have continued to compete with each other to not be named the most expensive of the largest supermarkets."
Download the LancsLive app for free on iPhone here and Android here.
To keep updated, follow LancsLive on Facebook and @LiveLancs on Twitter.
Have you got news for us? Contact our newsdesk on lancslive@reachplc.com.
Get all the latest news, sport and what's on stories sent to your inbox daily with the LancsLive newsletter here.
