VoIP provider Vonage has been hit with a potentially crushing court ruling for the second time this year.

The jury in a Kansas City federal court has awarded a $69.5m decision to Sprint, declaring that Vonage had infringed on its patents.

The figure represents five per cent of Vonage's revenues over the period in which it infringed on Sprint's patents.

"We are disappointed that the jury did not recognise that our technology differs from that of Sprint's patents," said Vonage chief legal officer Sharon O'Leary.

Vonage said that it will ask the court to set aside the verdict, and will launch an appeal if this tactic fails.

"Vonage has already demonstrated that it can keep its focus on customers and on its core business while managing ongoing litigation," said O'Leary, referring to the company's legal feud with Verizon.

Vonage was found to have infringed on Verizon's intellectual property and was forced to pay $58m in damages as well as 5.5 per cent of all future revenues. The firm warned in April that paying out the money could drive it into bankruptcy.

Vonage won a stay on the judgement in April, and the case is currently under appeal.