Sneaky, but legal, website tactics are infuriating online shoppers in the UK, according to research from Morecomputers.

The online and mail order supplier of computer hardware and software found that Briton's are becoming increasing angry about things such as hidden delivery costs and other hidden charges.

In a survey of more than 2,400 web users, the company found 93 per cent of online shoppers got annoyed when a so-called 'free delivery' turned out to require an extra purchase or spending above a certain amount.

Other frustrations include hidden surcharges for paying by credit card. Six in 10 online shoppers said when faced with this practice, commonly called  philfing, they refused to continue with the transaction.

This practice also meant online shopping comparison sites are now finding it increasingly difficult to maintain a level playing field when listing prices.

"We carefully monitor merchants for any signs of illegitimate or miss-leading behaviour," said Justin Sedgmond, merchant relations director for Pricegrabber.

"When we are made aware of any suspicious activity, we verify the problem and take appropriate action from there. We will contact the merchant, and solve the problem to make sure our customers are protected," he said.

Other things that annoy online shoppers include poor stock information, the lack of contact telephone numbers and the use of 0870 telephone numbers.

Brian Trevaskiss, operations manager at Morecomputers.com, said: ''Shopping online is without doubt quick and convenient. However, this growing trend of philfing is so annoying for consumers that they abandon their baskets at philfers' sites and shop elsewhere."

He said the company was also finding an increasing number of people are rebelling against higher rate telephone charges and using sites such as saynoto0870 to find a company's geographical numbers.