Facebook, we're told, is the office worker's favourite time-wasting website. But on one particular day of the year, employees put the social-networking site on the backburner and focus their attention on fantasy football, according to internet measurement firm Comscore.

On the Friday before the big Premiership kick off in August, over 230,000 office hours were spent on the fantasy football sites analysed by Comscore, with wannabe Wengers perfecting their first-choice eleven and tackling tricky dilemmas such as the relative merits of a 4-4-2 or 5-3-2 formation.

So what are the most popular fantasy football destinations? The Barclays Fantasy Premier League topped the list in August, with 1.36 million unique visitors. The Sun's Dreamteam website took second spot with 1.13m, while Fantasy League was third with 858,000.

Comscore said the figures prove that traditional social-networking sites such as Facebook and MySpace aren't having it all their own way when it comes to distracting employees from their work, although admits that fantasy football activity naturally tails off once the season begins. (I've not paid any attention to my team since a poor start to the season effectively ended my chances of winning PC Advisor's fantasy football superleague.)

The worrying thing for die-hard fantasy managers is that Comscore draws attention to the fact that almost 50 percent of the time spent tweaking fantasy teams during the week leading up to the Premiership kick-off was during working hours. And with businesses cracking down on the use of time-wasting sites during the working day, could fantasy football be the next target?