The majority of UK retail websites are leaving frustrated online shoppers stranded at the checkout because of the 'erratic functionality' of e-commerce shopping carts, a new report has claimed.

According to the E-commerce Performance Study 2004, conducted by web testing company SciVisum, 80 per cent of websites perform inconsistently, with widely varying response times, timeouts and errors, leaving consumers unable to complete their purchase successfully.

On average, UK shopping carts in the study were out of action for more than 10 times the accepted industry standard, the study claimed.

One in five carts did not function for 12 or more hours a month, while more than three quarters failed to meet the standard service level of availability of 99.9 per cent, equating to a maximum 43 minutes of accumulated failures a month.

"Many UK e-retailers have made significant strides in improving consumer experience, but the appalling state of other retailers' web services is both shocking and completely unacceptable. It blights our industry," said James Roper, chief executive of the Interactive Media In Retail group, in a statement.

Roper said the study indicated that bad website performance will cost merchants at least £225m this year alone if they fail to improve service levels.