Skype has announced the availability of four Wi-Fi mobile handsets for making free calls using VoIP technology. 

The four handsets are made by Belkin, Netgear, Edge-Core and SMC. The Netgear handset is already listed in the Skype UK Shop with a £140 price tag, but is marked as 'coming soon'. 

All four handsets come with the Skype software embedded, so a PC is no longer needed. Users can make and receive calls on the go, using any wireless internet connection, after entering their Skype username and password.

"We want to give people the freedom to move around while talking and have access to Skype wherever they are, whether in front of a computer or while moving around the home or office," said Skype general hardware manager Stefan Oberg.

The move is potentially worrying for the mobile phone industry, which is currently in bullish mood after better than expected quarterly results.

If VoIP Wi-Fi phones prove popular, and there is sufficient Wi-Fi coverage, people may no longer need to pay for mobile calls. 

The phones will work on encrypted Wi-Fi networks as long as a user has the proper network ID, but not on paid Wi-Fi systems like those offered at many bookstores and cafés. They are not designed to work seamlessly across multiple access points.

Skype first unveiled the Netgear VoIP handset at the Consumer Electronics Show in Las Vegas in January. 

Speaking at the time, Netgear chief executive Patrick Lo said: "We will free people from the inability to call people around the world because it's too expensive."

Lo explained that Skype Wi-Fi phones will be aimed at consumers rather than business users.

"The business community will require more upscale [devices]," he said. "You have to be able to roam between access points."

Skype is not the first VoIP provider to offer a standalone Wi-Fi phone, although it is the first to offer the service for free.

Vonage already offers such devices, but customers pay a monthly fee regardless of whether they call in or outside the network.