Online shipping is easy and convenient according to the consumer magazine Computing Which? But there are wide variations in the levels of service.

"Online supermarket shopping has become popular among people who don't want to face wonky trolleys, whining kids and checkout queues," said acting editor Sarah Kidner in a press release. "Although the quality of the sites varied, overall we found grocery shopping online to be easy and convenient."

Ocado, an independent company in which the John Lewis Partnership has a 40% stake, and WaitroseDeliver, which operates specific Waitrose stores and is owned by JLP, were voted top overall for best combination of ease of use and features.

Shoppers loved attributes like their 'excellent' search engines, which can work out what people are looking for even if spelled wrongly, such as figuring 'obergine' meant 'aubergine'. Other sites floundered on this; Asda and Sainsbury, for example, couldn't cope with wrongly-spelled words.

One drawback to online shopping is not being able to see whether an item is in stock, as you would in the shops, the magazine said. Ocado is the only site that tells shoppers if something's unavailable before they choose to buy, but once bought, only Tesco allows customers to suggest a substitute item should their first choice be out of stock.

Information about ingredients and nutritional content varied greatly. A poor example was an Asda ready meal for which the only additional information was 'ASDA Indian meal deal for one, 642G'. Tesco's information was also limited, but Sainsbury's and Ocado were good and WaitroseDeliver even listed storage and cooking instructions.

Ocado, Tesco and Waitrose all offer good-quality pictures of products, which can be a help if people want to read labels or simply see what a product looks like. Asda lets pictures be turned off altogether; handy for users with slower dial-up internet connections.

Although there are obvious drawbacks to shopping online as opposed to being in the shop — for example, none of the stores list Best Before dates, so there's no way of knowing products' shelf lives - overall shopping online was found to be easy and convenient, and all the websites received a good general satisfaction rate.