Mobile phone services company FastMobile has launched Fastxt, its state-of-the-art technology which brings instant messaging to mobile phones.

Over 5.5m internet users are currently signed up to instant messaging services, including MSN and AOL's Aim, allowing them to chat in real time without any delays or interruptions to their friends and family.

But mobile users have thus far been stuck with SMS, which although fairly reliable is subject to delays due to busy networks, limits users to small file sizes and maximum characters per message and comes with a hefty charge of around 12p for each message sent.

FastMobile's Fastxt allows customers to chat with several friends at the same time and each message costs less than a penny because it uses GPRS (general packet radio services), so-called 2G, which sends data at high speeds and doesn’t rely on busy networks. Furthermore, there is no limit to message size, so users can chat as long or as little as they choose.

"We believe that fastxt is the first of many killer applications that FastMobile can deliver over 2.5G and 3G mobile networks," said Patrick Pollard, managing director of BlueStar Ventures, one of the companies supporting the launch.

The Fastxt service costs £5.99 a month, but is currently only available on Nokia's 7650 handset. The service will be extended as new Smartphones are released.