The papers would blush but anything goes on their websites

In-your-face celebrity stories have helped push Mail Online to the top spot for users, but do the figures tell the full story? asks Joy Lo Dico

It was a picture that would make many blush: Cristiano Ronaldo, in swimming shorts, nestling between the legs of his bikini-clad girlfriend on a beach in Sardinia, a fig leaf for her dignity. The Daily Mail ran it on page 23, in among other less racy shots. On the Mail Online website, it was unavoidable at the top of the homepage.

One can't imagine Daily Mail editor Paul Dacre, a man of sound family values, putting it on the cover of his newspaper, but the recently relaunched Mail Online isn't so shy. With Martin Clarke, a hardball Associated Newspapers veteran at the tiller, the website isn't scared of putting celebrity above the fold, digitally speaking. Along with the Ronaldo snaps on Thursday, readers were just a click away from stories on David Beckham taking his children for a spin in a Rolls-Royce, Princess Beatrice having shoe trouble and Amy Winehouse on the booze, all with pictures attached. You had to scroll down a pretty long way to find columnist Melanie Phillips.

This distinct move has done wonders for the Mail's online circulation. In the May ABCs – the Audit Bureau of Circulations measurement of traffic to the newspaper websites – it leapfrogged the Telegraph and Guardian to take the top spot with 18.7 million unique users, an impressive achievement for a website that only really geared up in 2006.

The site comes with the blessing of Dacre, who oversees it as editor-in-chief of the Mail group but has not previously been known for his internet nous. "He's the one," says Martin Clarke, digital director of Mail Online. "It was his decision to put steam behind it, he's driven it ... We are not betting the farm on digital but it's obviously part of our future."

The Mail's new digital confidence has shaken up the ABCs. The Telegraph, which had taken top spot in the previous month, came in second with 18.4 million, while the Guardian, the long-standing leader, slunk in at third with 18.3 million. The Sun, which has been heavily promoting its celebrity content, had 15 million unique users. (The Independent made its debut in the ABCs with six million readers.)

Already the internet talking-heads are complaining that the Mail's sudden ascendancy is based on cheap numbers. Of its 18.7 million users, only five million are UK based, a smaller proportion than any of its rivals. Mike Butcher, editor of the Tech- Crunch UK blog, suggested in a recent article that the Mail's success was down to "link-bait". When big US celeb blogs TMZ and Perez Hilton link to a celebrity story, tens of thousands of followers from around the world stop by for a quick rubberneck.

Clarke is riled by the implication. "He doesn't have access to the numbers," he counters. "The hard news does more traffic than celebrity photos. I can tell you our news traffic has grown just as much as celebrity and sport."

While Clarke may not acknowledge it, others recognise that big US blogs are ramping up the figures. Pete Picton, editor of The Sun Online, says that when US website The Drudge Report picked up its UFO front page story on Wednesday, its site saw a 169 per cent rise in traffic. The Telegraph also knows the game.

"I think it is a reality that the Mail and others, including ourselves included, get a lot of traffic from Drudge, Digg and Fark," says Ed Roussel, the Telegraph's digital editor.

"There's two ways of looking at it. One view is that thist traffic hasn't got a lot of value – you are in and you are out. The other view is it's a great way to introduce your web content to an international audience. We have six million unique users in the US. Some of them have bookmarked us and visit regularly."

The Telegraph, too, is not ashamed of using celebrity content or quirkies, another favourite of the big blogs, to drive traffic. "There are other types of content which we would not necessarily include in the newspaper – stories with a lot of humour, some showbiz. We experiment with that, and we are keen to do that in a way our readers would like, adhering to good taste," Roussel explains.

The rival that should be most shaken by the Mail's ascent is The Sun Online, a natural home for the celebrity story. Picton, however, says it is far more focused on UK readership, which stands at over five million. "If you look at the site in the office and again at home, you count twice in ABCs. Many of our readers aren't in offices so we get penalised. But if you look at UK users only, we beat the Mail. If you look at Comscore [a user-focused survey], we beat them again."

The significance of the US share of audience is one of a growing list of disputes over figures. When the Telegraph took the lead in April, gaining five million users in a month just months after it switched data-collection agencies from Hitbox to Webtrends, the Guardian ran an article saying that ABC would be reviewing its measurement standards. Clarke at Mail Online is also cynical: "We use Intellitracker. But if I can find five million down the back of a sofa, I'd change."

Roussel says the move was within the rules, and the growth has been consistent. "There's a certain amount of sour grapes," he says. "We were the first to overtake the Guardian."

All three papers are relatively new to the web game in comparison with the Guardian, which has been steadily expanding its website since the turn of the century with a "why wait?" philosophy behind it. The Guardian lost 1.2 per cent of its unique users in May but year-on-year has added 14.1 per cent without the aid of "link-bait" of the order of Perez Hilton or Ronaldo in anything less than a football strip.

"We are not complacent," says Emily Bell, director of digital content for the Guardian. "What we do in journalistic terms is strong and we are investing in journalism. We are not about to tear up the blueprint and get in lots of picture galleries of Amy Winehouse and say 'forget Afghanistan'."

In another way of cutting the statistics, Technorati, a blog indexer, notes that there have been over 460,000 blog reactions to Guardian articles, proving both engagement in its output and its authority. The Telegraph and the Mail Online do not reach half those figures, and the Sun only around 60,000.

It's these kind of statistics that may fare better as advertisers start to look for readership quality as well as raw numbers. Next year the Joint Industry Committee for Internet Measurement Systems, made up of advertising and online publishers, will launch a system of data analysis more akin to the National Readership Survey than the ABCs. It will also focus entirely on the UK.

However, it unlikely to dent the the bullishness of the Mail. "All we've done is build a foundation," says Clarke. "We don't think we've done any more than scratch the surface."