Forget the youth club — record numbers of children are spending their leisure time exploring online worlds that combine the fantasy element of traditional games with social networking. The games mark a shift in the industry away from adult-oriented virtual reality adventures and towards less gritty and more fun titles aimed at pre-teens.

The popularity of these games has surged in recent months as word of mouth spreads. Two sites stand out: the Disney-owned Club Penguin attracts an estimated 4m primary-school-age children every month, and Habbo Hotel has signed up 120m teenagers worldwide. These are figures that dwarf much-hyped adult worlds such as Second Life, which has never drawn more than 2m users in a month.

Unlike Second Life, they also make big, real-world money: although they are free to sign up to, players must pay hard cash to access extra features or buy online products. Pester power has resulted in some parents paying a subscription of around £4 a month that allows unrestricted access.

Cash-strapped parents are about to get a break, however. Last week a huge new online game world, Free Realms (www.freerealms.com), was launched, offering much more play completely free of charge. Designed by Sony Online Entertainment, Free Realms takes the look and feel of the popular adult online game World of Warcraft and adds a lighter, knock­about tone. Young players can explore the vast game space with their friends, or undertake quests in the company of computer-generated characters. They can e-mail and chat and plan their next adventure together.

It’s very child-aware: players can’t use their own names and there are ­severe restrictions on chat facilities for anyone under the age of 13. The result is an ingenious blend of a role-playing game and social meeting place — and it’s hugely addictive.

That addictiveness is central to Sony’s ambition. Despite being billed as “completely free”, the game will have some subscription elements — though far fewer than its rivals. For $4.99 (£3.30) a month, members get access to magical items, can see their screen names on leaderboards and, most important, can take on new jobs. In Free Realms, players can be anything from a racing driver to a chef, but only nine of the 14 jobs are available to non-members — and completing every mission in every role is one of the game’s main hooks.

Free Realms isn’t the only new game chasing a pre-teen audience. Coming next year will be Lego Universe, in which players fight pirates and robots. Maybe the kids are onto something.

How free realms works

A range of features keeps things simple for younger players, such as dotted pathways that lead to your next objective, and step-by-step instruction panels detailing your current quest.

You can borrow pets from other characters, but if you want your own moggy or pooch you’ll have to pay real cash for the privilege.

Players can chat to one another as they play via an instant messaging system, or send in-game e-mail messages.

New players construct their online character from a selection of faces, hairstyles and clothes. There are two races — human and pixie — to choose from.