Tesco Direct was the best performing UK retailers' website over Christmas, according to monitoring data released today.

Keynote Systems said that the retail giant topped the league in terms of site responsiveness and reliability among 16 leading UK retail sites between 7 December 2007 and 7 January 2008.

The monitoring included Argos, BBC Shop, Amazon, HMV, Tesco Direct, Woolworths, Virgin and Play.com, among others.

The BBC Shop topped the overall reliability chart with a "staggering" average of 99.9 per cent throughout the study period.

This was followed closely by Play.com with an equally impressive average availability of 99.6 per cent.

The industry average is 97.7 per cent, a performance exceeded by Pixmania, Tesco Direct, ASDA and Comet, which points to a generally good level of site management by some of the leading UK players.

Argos beat John Lewis to the top spot in overall responsiveness with an average load time of 0.74 seconds per page.

John Lewis recorded a load time of 1.04 seconds per page, compared to the industry average of 1.5 seconds, with the poorest sites averaging over four seconds.

The best overall performing site was Tesco Direct, however, despite finishing fourth in both responsiveness and reliability.

Ben Rushlo, senior consulting manager at Keynote Systems, said: " Unfortunately basic load testing alone is no longer adequate to determine how well your site will perform on the internet.

"Sites need to simulate the dynamic nature of the internet, using actual web logs and comprehensive research to accurately and realistically model varying number of users, including flash crowds, which are inevitable at certain points during the year.

"Christmas is a time when most websites peak and traffic increases d ramatically, so you would expect large retailers to fully test their sites in preparation, but it seems some do not.

"In a competitive market such as this, website performance can be the difference between retaining a customer and losing them to a rival.

"Sites such as the BBC Shop, Play.com, Argos and John Lewis all deserve to be credited for their individual performance achievements but it is not just important to top one of our rankings.

"A site like Tesco Direct may not hold top place in either of the rankings but overall it is the site providing its users with the best online experience.

"As a company's website ultimately represents the company, it should be given the same care and attention as a member of staff, as it can be the first port of call for potential and existing customers."