Websites of the UK's top retailers were unavailable to customers for the equivalent of three days a year says a new survey published yesterday.

Their performance was amongst the poorest of the UK's 100 largest companies according to network-management company Parallel, which measured areas such as site availability and download times across the sites studied.

Marks & Spencer Plc had the worst performing retailer site, with 98.16 per cent availability.

A recent survey conducted by Forrester Research found that 58 per cent of Internet users in the US and Canada said they were unlikely to return to a site where they had problems on the first visit.