'Bad sites selling bad goods': Which? pans online grocers

Based on 40 online shopping trips, the Which? panel of 25 assessors found the main problem was with the time taken to order - over half the orders took over an hour and a half to complete. This was partly due to sites crashing.

However, one Tesco shopper reckoned that she could do her weekly shop in just half an hour.

Another gripe was the choice of substitute items when the original choice was unavailable and most complained of being sent items which were close to their sell-by dates.

The top four grocers featured - Tesco, Sainsbury's, Asda and Iceland - were all rated as adequate to satisfactory in their delivery, with all four pledging to do better still.

A spokesman for Sainsbury's said: "We are constantly improving and updating the service and we always aim to provide shoppers with the best quality products." His words almost echoed those of a spokesman for Asda who said: "We have thousands of happy shoppers who are enjoying the benefits of shopping with Asda at home and we are improving the service all the time."

Tesco is currently the most successful online supermarket with 750,000 registered users placing 60,000 orders a week, which equated to £250m-worth of online grocery sales last year.