Metro's website traffic has plummeted by 37 per cent in a year, according to ABC figures.
An average of 925,535 daily unique users visited Metro.co.uk in September, down 34 per cent on August. Metro had been consistently the fastest growing UK national newspaper website before its editorial team merged with sister title Mail Online last year.
The next worst performing website, in terms of year-on-year change, was the Mirror, flat on 3.9m unique users a day.
Mirror Online editorial director Pete Picton said this was explained by an "extraordinary September 2014 which saw a story about Jennifer Lawrence go viral around the world. That article remains the most clicked on Mirror.co.uk story in history."
September saw all tabloid newspaper websites except the Express lose readers compared with August.
The Daily Star's website was down 35 per cent to 570,609 and Mail Online, the UK's largest newspaper website, was down 2 per cent to 13.3m. Mirror Online's 9 per cent drop was explained by the end of the football transfer window and a "relatively quiet news month".
The Sun's loss of 14 per cent saw it drop below Express.co.uk again after ovetaking the site in August. The Sun's website was audited by ABC for the first time in two years in July, recording just under 800,000 unique daily users. In August, The Sun's website was the fastest growing of all nationals, up 63 per cent.
The Guardian and Independent were the only national newspapers to see their website figures grow month-on-month in September, according to ABC figures.
TheGuardian.com attracted an average 8.4m daily unique users last month, up 11 per cent on August and 29 per cent on September 2014. The Independent's website, meanwhile, was up 10 per cent month on month and 16 per cent year on year to 2.8m.
The Guardian said in coverage of the discovery of water on Mars "drove significant traffic". It said in a statement: "?Other stories which proved popular with readers included ?an interactive on affordable housing and live blogs on the Labour leadership election and the Rugby World Cup."?
|Website||Average unique daily users, September 15||Month-on-month % change||Year-on-year % change|
|Trinity Mirror Group – Digital||5,702,533||-8.1|
|Mirror Group Nationals||3,894,176||-8.77||0.28|
|Trinity Mirror Regional Network||2,050,892||-7.29||52.11|
|Manchester Evening News||582,672||-8.31||49.74|
|Teesside Evening Gazette||97,749||4.56||55.66|
|Daily Post (Wales)||74,912||-0.87||99.66|
|Huddersfield Daily Examiner||62,134||17.1||52.12|