The liquidators of Hellas Telecommunications, which was once the third-largest cellular service provider in Greece, are suing its former private-equity owners TPG Capital Management and Apax Partners for what it calls "one of the very worst abuses of the private equity industry."

In a lawsuit filed Thursday afternoon with the US Bankruptcy Court in Manhattan, the Hellas liquidators alleged that Apax and TPG carried out a "highly leveraged acquisition of a pair of Greek businesses," and then syphoned more than €1 billion out of the companies. The other company acquired, identified in the complaint, is Q-Telecom.