Skype has stopped supporting the Fring application released last week to allow iPhone 4 owners to make 3G video calls to Android and Symbian devices.
Fring temporarily reduced support for Skype on Friday in a bid to ease "network stress" caused by the high volume of video calls being made. However, Skype has since refused to restore support, and has threatened legal action against Fring.
Fring expressed its disappointment about Skype's "anti-competitive ambush" and the ending of the firms' four-year partnership.
"Despite Fring expanding its network capacity over the last days to serve its enlarged user base, Skype is refusing to allow Fring to restore connectivity to Skype," said Fring in a statement.
"Fringsters will no longer be able to communicate with their Skype friends the way they want, but can invite their Skype friends to join Fring and enjoy unrestricted mobile video calling from any mobile phone."
Skype once championed the cause of openness, but is now attempting to " muzzle" any competition, to the detriment of its own users, argued Avi Shechter, co-founder and chief executive of Fring.
Shechter apologised to users for the impact of Skype's "bullying", and said that Fring will be happy to reconnect with Skype once it reverses its decision.
"We believe in communication openness and know that users will continue to vote with their mobile phones, opting for Fring's innovation, clarity, honesty and openness," he added.
Skype countered that it has not blocked Fring, and that it was Fring's decision to remove support for Skype.
It added that Fring's "misuse" of Skype software was "increasingly damaging our brand and reputation with customers".
"On Friday, Fring withdrew support for video calls over Skype on iOS 4 without warning, again damaging our brand and disappointing our customers, who have high expectations of the Skype experience," Skype complained.
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