The surging uptake of VoIP technology may mean the end of traditional landline and mobile services, according to consumer body Which?.

"Pricey landline and mobile bills could be in danger of becoming extinct," said Computing Which? editor Jessica Ross. "With mobile phone services entering the broadband market, VoIP looks set to be the choice of the future."

Ross's comments follow a new Which? survey of free VoIP services, which compares six free internet telephony services for ease of use, effectiveness and range of features.

Skype takes the top spot for its "fuss-free approach, easy set-up and exceptional voice clarity", while Yahoo Messenger is commended for its range of features, including voicemail and conference calls.

MSN Messenger and Sipgate also rank well for features including an audio wizard sound-optimiser.

Google Talk fared less well "with audio level indicators only kicking in once the call had been initiated", and Babble.net is described as being "let down by poor help files and software bugs".

Which? researcher Kim Gilmour, part of the VoIP testing team, told vnunet.com that the growth of internet telephony may even speed up over the coming year.

"VoIP is growing at a huge rate already. Skype's figures speak for themselves. At any one time there are five million people online using Skype, and it's still a relatively new technology," she said.

"A recent survey of our online users found that 12 per cent are already using VoIP. As more people sign up for the services that let you make free calls to someone with the same software, it will probably grow even faster."

The big telcos have been left playing catch-up. "BT now has its own version, after getting together with Yahoo for its BT-based VoIP service. I cannot comment on the quality of that service yet, because we only included free services this time," said Gilmour.

Which? has published an online VoIP comparison chart of all current VoIP services available in the UK. The table is free to view by magazine subscribers and non-subscribers.