Mark Main, an analyst at Ovum, estimated there were 500,000 VoIP users compared with tens of thousands when Ofcom looked at the market 18 months ago.
"At the time only Skype and BT had products in the market, which has grown about 20-fold since," said Mr Main. In the past year, these two operators have been joined by other big names, including Vonage of the US; Wanadoo, a unit of France Telecom; and Tesco.
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