Steve Jobs has said that developers will only be allowed to develop voice over IP applications for use over Wi-Fi rather than over GSM or EDGE networks on the iPhone.
The comments were made at the company's town hall event at the launch of the software developers kit for the Apple iPhone.
It's thought this stance is an attempt to protect Apple's revenue sharing deals with mobile phone operators around the world, and is likely to infuriate VoIP companies and users looking to get calls on the cheap.
Apple is rumoured to get as much as 40% of revenue from of all calls made on the handset and it likely to want to protect this as best as it can.
Last year Truphone lambasted Vodafone, Orange and T-Mobile for disallowing its software to run on the Nokia N95 handset.