New advertising-supported free mobile phone network Blyk officially launched at a press event in London's Soho this morning.

Aimed at 16 to 24-year-olds, Blyk is an invite-only service that gives its users free texts and voice minutes every month. You'll get 217 free text messages and 43 minutes of free calls (domestic UK mobile and landline calls only) every month. The figures have apparently been worked out through years of market research into how young people use their mobiles.

If you exceed your monthly allowance you can top up with more credit on Blyk's website. You won't get a phone bill; the service is available on a pay-as-you-go status only. Text messages are priced at 10p and voice calls cost 15p per minute.

Invitation

You can receive a Blyk invitation either by sending an SMS text message containing the word FRESH to 82595, or by someone inviting you to join the service. You'll then need to enter key information about yourself, your hobbies and habits when it comes to shopping, surfing the web and so on. This information is used to build a profile of you so you can be targeted with relevant advertising only.

You'll be sent your Blyk SIM card in the post - you can keep your old number if you like. When you start using the service you'll receive up to six advertising messages - as MMS messages, formatted as surveys, invites or video clips - throughout the day at set times.

For example, a young woman interested in fashion may be asked which celebrity outfits she likes best, and so on. After a few messages back and forth, there will usually be some kind of discount offer or special invitation to an event. These interactions are free for the user. Some 40 brands - including Adidas, Boots, Coca-Cola, L'Oréal, Sky and Xbox - are already signed up.

"We found that what is 90 per cent familiar and 10 per cent new leads to the best user experience," Antti Öhrling, co-founder of Blyk, told Tech.co.uk at this morning's briefing.

"So, the Blyk communications formats are based on the most dominant and most familiar pattern among 16 to 24-year-olds; getting a message and responding to it. Using both pictures and text."

MMS only requirement

There are no specific requirements when it comes to compatible handsets - you won't need a smartphone or 3G connectivity, you just need to be able to receive MMS messages.

Blyk would not confirm whether there would be any rewards for people inviting friends to join the service. "There may be [rewards]," Leif Fågelstedt, Blyk COO and managing director for the UK, mysteriously indicated to us after the event.

The service launches in the UK today, picked because it is "the biggest advertising market in Europe". "The plan is to become a pan-European service," Fågelstedt said, without giving a specific timeframe.