Nokia and Orange have both denied that the move is a deliberate attempt to defend voice revenue and head off competition from cut-price internet telephony.
A Nokia spokeswoman told vnunet.com that Orange had asked for the VoIP functionality to be switched off, but added that it is not Orange's policy to remove VoIP from devices.
"This a handset-specific issue," she said. "In this particular instance Orange was asked by Nokia whether they wanted the functionality switched on or off, and Orange selected off."
A spokesman for Orange maintained that the decision was taken because there was too little time to test the application thoroughly. Future handsets might have VoIP enabled, he claimed.
Vodafone said in a statement that the operator does not offer its own VoIP service because the technology is not yet mature.
Internet telephony, according to the statement, requires "in-depth testing, a solid end-to-end customer experience, billing integration and customer service support which is not currently available".
"Customers can download VoIP applications if they choose to do so or can use VoIP services via a laptop and data card," the statement added.
However, internet telephony firm Truphone claimed that the move is an attempt by mobile operators to stop open competition for mobile internet services and to lock customers into their services.
"The danger is that the net neutrality we enjoy and take for granted with the internet on PCs will not be replicated in the mobile world," said a Truphone spokeswoman.
"By effectively denying oxygen to, for example, fledgling VoIP service providers on the Nokia N95, the mobile operators concerned are forcing us into their walled gardens.
"If this is successful [from the operators' perspective] it is likely that this situation will be replicated on other handsets and other networks, and even for other services.
"This will be disastrous for the consumer; the best way to encourage innovation and lower prices is through fair competition."
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