Facebook has gained ground on its News Corp-owned social networking rival MySpace, which suffered its first monthly drop in traffic in almost a year.

The number of unique UK visitors to MySpace declined by 300,000 to 6.5 million in May against the previous month, while Facebook gained 527,000 visitors over the same period, according to Nielsen//NetRatings.

Facebook attracted 3.2 million unique UK visitors in the month, with 10 percent of the population logging on. Bebo, the third-biggest social networking site and particularly popular with teenagers, has experienced steady growth since April, with an audience of 4 million in May.

MySpace's unique US visitors declined by 450,000 to 56.6 million in May, while Facebook's US audience has grown by a similar margin to 14.2 million.

MySpace is more dominant than Facebook in the US, with an audience four times the size of its rival. In the UK, MySpace is only twice as big as Facebook.

Alex Burmaster, European internet analyst at Nielsen//NetRatings, said: "MySpace is, by far, still the most popular social network. However, if last month's growth rates were to remain consistent, both Bebo and Facebook would catch MySpace in September this year.

"Meanwhile, MySpace does trail the other two when it comes to user engagement. Bebo leads the way, with its average visitor spending just over an hour and a half on the site - almost 10 more minutes than the average 'Facebooker' and almost a whole hour more than the average 'MySpacer'."

Contact: Lisa Simmons