Good Housekeeping magazine found shopping over the internet took an average of 46 minutes.

But physically going to the store could be done in just 37 minutes.

The website with the worst result was Sainbury's - orders took an average 68 minutes to complete.

"A service which is based on convenience and speed should be catering more for consumers on all fronts," says Good Housekeeping editor Lindsay Nicholson, "and not becoming a stress-filled chore which takes longer than a trip to the supermarket."

The magazine asked researchers to order 26 items from five online sites.

None of the orders was delivered exactly as requested - and two didn't turn up at all. The findings included:

Had the largest number of delivery slots but items were missing from every order and some people received goods they hadn't requested.

Had lots of delivery slots, but the site was slow to use - one order took two hours to complete. Fresh produce was of poor quality.

Site was the easiest to use but hard to find delivery slots, especially at weekends. Freshness of produce generally good.

All deliveries were on time but a lot of produce was poor quality - the mushrooms contained a dead fly. Highest level of missing and substituted goods.

This service had the best all-round results, with well-chosen goods and few missing or substituted items. But there were some technical problems with the website.

Retail analyst Richard Perks of Mintel is not surprised by the findings.

"Yes, it is slow, it is unreliable, they are not always actually meeting the delivery slots that they hope and they're not that good at getting the replacements right," he says.

I just don't think that people really like shopping from home very much. They like to get out there and touch the products and see what they are buying first. Richard Perks, Mintel

"But a lot of people are using it. We do a survey every month and about 6% of those people who have got internet access are using the service.

"The trouble is that proportion has stayed pretty much constant for a year and a half, so they're not making any more inroads."

But some stores have made the service work well - Tesco's is profitable, with a turnover of �450m.

On the other hand, Safeway shut down its online store after six months, saying the money could be better used in its shops.

Ocado, which did the best in the survey, says that's because it uses a central warehouse instead of picking items off the shelves of a supermarket.

"We can operate a better level of customer service because we have all our stock consolidated in one place," explains chief financial officer Jason Gissing.

Jason: Consolidated stock

"When you come online and place an order we can tell you whether you have it or not. That way you get what you actually ordered."

Ocado, which delivers Waitrose products, currently serves only Greater London and Hertfordshire.

Richard Perks believes scale is vital for its model to work successfully.

"If you don't have enough volume going through the warehouse then the sums aren't going to add up - it's just not going to be economic," he says.

Online shopping is still in its infancy in the UK compared to the US. Only one in 10 online consumers shops on the net in this country.

Broadband

Richard Perks thinks there are technological and cultural hurdles to overcome to achieve greater growth.

"There are going to be people who really do want their groceries delivered every week, but there aren't going to be many," he says.

"If you're really going to use this and it's going to be user-friendly, you've got to have broadband and not very many people have broadband yet.

"But I just don't think that people really like shopping from home very much.

"They like to get out there and touch the products and see what they are buying first and I think that's the biggest handicap any home shopping service is going to have."