While The Guardian remained the most popular site at the end of 2007, unique users to the site dropped by 8.8 per cent to 15,955,312 from the previous month - the lowest number for the site since August last year.
However, the site showed a 21.2 per cent increase in unique users since December 2006.
Page impressions for the site in December also fell by 14.6 per cent to their lowest figure since February - 136,971,765.
Telegraph.co.uk was hardest hit in December recording the biggest drop in unique users - around 2.3 million to 10,549,554 - making the site the fourth most popular of those measured.
Similar declines in unique users were recorded for The Sun and Times' websites with 11,173,492 unique users for Timesonline over the period - a decrease of 9 per cent - and 10,474,814 for The Sun, which lost 1,133,893 unique users.
Despite recording the lowest figures of the five sites in December, the latest figures show a 45 per cent growth in unique users for The Sun site year-on-year.
The Daily Mail held on to second position behind the Guardian recording the smallest change in unique user figures - a fall of 785,903 to 13,629,821 - and page impressions, down 9,203,004 (8 per cent) to 105,981,970.
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