Asda, Morrisons, Sainsbury's and Tesco are lagging behind Aldi and Lidl in annual supermarket survey
The so-called Big Four supermarkets have slumped to the bottom of an annual ranking after disappointing customers with the quality of their food and ability to keep up with online rivals.
Asda, Morrisons, Sainsbury's and Tesco are all in the bottom five, along with Iceland, for their in-store offer in the Which? survey after achieving low scores for their produce and own-label lines.
Discount supermarkets Aldi and Lidl both outperformed the Big Four with scores of 68% and 66% respectively, and both received five stars for value for money.
Asda achieved the lowest score of 56% for in-store shopping and 65% for online shopping after managing just one star for the quality of own-brand items and two stars for freshness of produce.
Which? said Asda's online customers reported that it was unusual to receive a delivery without a substitution.
Some 55% had received a substitution with their last order, including parsley replacing basil, potato gratin instead of macaroni cheese, and red wine vinegar replaced by a bottle of red wine.
Tesco scored just above Iceland and Asda at 59% for its in-store offer, achieving just two stars for value for money with some survey respondents reporting concerns that it was becoming more expensive, but performed better for online shopping with a score of 71%.
Sainsbury's achieved 63% for its in-store offer and 69% for online shopping, but customers awarded it only two stars for value for money in both categories.
Morrisons won the highest scores of the Big Four at 64% for in-store shopping and 70% for online but was let down by the two-star rating of its own-label products.
Iceland came second to bottom in the ranking with a score of 57% for in-store shopping. However the popularity of its online offer took it to second place only to Ocado with a score of 79%.
Waitrose topped the table for in-store shopping, receiving five-star ratings for store appearance, queuing time, staff availability and range of product but achieved just two stars for value for money.
Which? Magazine editor Harry Rose said: "Our survey shows that while the Big Four are failing to consistently give customers the high-quality experience they deserve, both in-store and online, no supermarket is getting everything right.
"People today have more choice than ever on where to do their food shop and staying loyal to one supermarket has become a thing of the past. The big supermarkets really need to up their game if they're going to keep their customers coming back."
An Asda spokesman said: "Whilst we're disappointed to see that some Which? readers haven't had a good experience with us, other independent surveys, such as YouGov, rate Asda as the second most recommended supermarket and our own measures show that Asda shoppers are enjoying shopping with us more and more each year."
Which? surveyed more than 12,000 of its members in October and November.