The outlet's daily web traffic dropped to 1,117,256 unique visitors last month, a 22.96 per cent decline from November. It was also the only publisher to report a year-on-year drop in daily readership, of 5.29 per cent.
The Telegraph had the second sharpest decline in online traffic – 4,038,417 people visited the website in December, going down 19.59 per cent since the previous month, when it passed the 5 million daily readers mark after investing heavily in its digital operations.
Elsewhere, the average number of daily browsers at The Express declined by 18.72 per cent, to 1,065,378 readers from 1,310,798 in November. However, the title still has the highest year-on-year growth rate, of 44.62 per cent.
The Mirror's online traffic dipped by 15.79 per cent, to 3,994,246 readers in December, after growing in November due to rolling coverage of the Paris terror attacks.
The title's busiest traffic day over the Christmas period was Boxing Day, Pete Picton, editorial director of Mirror.co.uk, said in a press release.
"Our technology and science team’s exclusive on hackers tracing Isis email addresses back to the Department of Work and Pensions was one of the top five most popular stories," he added.
The Guardian lost 15.40 per cent of its daily online readership last month, reaching an average of 7,847,537 readers, compared to 9,276,546 in November.
And some 2,796,267 people read The Independent's website in December, down 14.68 per cent from the previous month.
MailOnline, The Daily Star and The Sun registered the lowest drop in daily traffic last month, of 9.90 per cent, 8.80 per cent and 5.63 per cent respectively.
MailOnline retains its position as the most read UK title, with an average of 13,182,486 daily visitors, a 7.67 per cent increase year-on-year.
The Sun averaged 1,525,662 daily readers last month, down from 1,616,705 in November.
However, it has seen a considerable increase from its initial readership of 792,994 six months ago, when it started making some of its online content available for free before scrapping the paywall altogether towards the end of 2015.
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