The proposed purchase of Skype by a prominent group of investors hit a stumbling block from a move on Wednesday in which a company owned by Skype’s founders sued current owner Ebay, the investor group and Skype for copyright infringement.

Joltid, a company run by Skype founders Janus Friis and Niklas Zennstrom, is seeking an injunction in the US that would stop Skype from operating and recoup damages it says are accumulating at a rate of more than $75m per day.