The increase puts it in front of rivals such as Bebo, with 9.3 million users, and Facebook, which boasts 4.8 million users.
MySpace has made its name by catapulting the Artic Monkeys to fame. But it is not only a site for new and established bands. MySpace is also a place where marketers can promote causes likely to appeal to the young.
The website's top two spots among UK surfers are Red, and the campaign to buy ethical goods to help HIV sufferers in Africa supported by Bono.
Networking websites such as MySpace enable users to contact each other, form networks of friends, plan diaries, share photos and, in some cases, swap videos.
MySpace was bought by NewsCorp two years ago and is popular among late teens, while Bebo is more popular with schoolchildren. Facebook has tended to attract users among older age groups.