Guardian Unlimited and Times Online achieved record online readership in January, according to ABCe figures released this week.
Guardian Unlimited posted 15.7 million unique users globally in January, up 19.7 per cent year-on-year.
In its last ABCe figure before its February relaunch, Times Online reported just under 10.9 million unique users in January, a figure up just over 40 per cent year-on-year.
Guardian Unlimited also provided a breakdown of its figures to highlight its readership within the UK. About a third of Guardian Unlimited's audience, 5.4 million unique users, were based in the UK, up 26.2 per cent year-on-year.
Comparison with other national newspapers' sites is not possible because only The Guardian and News International regularly publish ABCe-audited figures.
Tom Turcan, general manager for Guardian News & Media's digital operations, called on the industry to rally around ABCe-audited figures as a "common currency" for web metrics.
"To make claims based on proprietary systems which not everyone is using and have different characteristics will have the effect of confusing our nascent market," Turcan told Press Gazette.
One of the "proprietary systems" is the online competitive intelligence firm Hitwise, which this week released figures painting a very different picture of the national newspapers' online readership.
Hitwise's data, based on a "networkcentric" methodology that collects data about UK traffic from internet service providers rather than publishers' own server logs, shows DailyMail.co.uk rising from ninth to fifth in a market-share league table of news websites associated with print titles, with 68 per cent yearon- year increase in market share.
Hitwise lists Guardian Unlimited dropping from first to third in the past 12 months and shows Telegraph.co.uk moving from fourth to first.
These figures, which have been cited in a high-profile advertising campaign by The Telegraph, have been disputed by both The Times and Guardian.
The row has led to a complaint to the Advertising Standards Authority over The Telegraph's claim to be the UK's "number one" quality newspaper website.
Turcan told Press Gazette that in the absence of industry agreement on standard metrics, these recurring arguments over competing statistics is merely "internal willy waving between the media owners" that does not reflect the commercial realities of online competition.