OTE, Greece's largest telecom group, which is partly owned by Deutsche Telekom, may sue Siemens for damages for allegedly overcharging, a Reuters report said.
The report quoted German newspaper Sueddeutsche Zeitung saying that OTE has contacted lawyers in Germany and Greece to examine and prepare all necessary steps, which include a claim for damages.
Siemens was not immediately available for comment.
Earlier this week, former Siemens manager Reinhardt Siekaczek told a court that he had been asked by superiors to construct a slush-fund network to disguise payments to foreign telecoms companies after such bribes became illegal in Germany in 1998, the report said.
Such payments may have helped Siemens' telecoms equipment division, of which OTE was a major customer, win contracts against rivals such as Cisco , Nokia and Ericsson, the Reuters report suggested This is bad news for Siemens which is already embroiled in court cases over alleged bribery and fraud.