Telekom has admitted that it hired an outside firm to track hundreds of thousands of phone calls by senior executives and journalists to identify the sources of press leaks, but said the "ill-advised use of communications data" happened only in 2005 and probably 2006.
But Hans-Jürgen Knoke, who was responsible for security at Deutsche Telekom from 1998 to 2004, told the Spiegel television channel that the company was already engaged in the practice under former boss Ron Sommer, who left the group in 2002.
"The management had expressed its discontent that internal information was being leaked non-stop to the press. There was gossip and still more gossip, something new every day," he said.
It was then decided to monitor who had access to documents and maintained contacts with journalists, Knoke added.
Meanwhile the weekly Der Spiegel, in its edition appearing on Monday, alleges that two more former Deutsche Telekom bosses, Kai-Uwe Ricke, who stepped down in 2006, and Klaus Zumwinkel, who headed the supervisory board, are in the spotlight of prosecutors.
Quoting prosecution documents, the magazine says another former Telekom security chief, Klaus Trzeschan, had alleged he had been ordered to spy by Ricke and Zumwinkel, but that they had not been informed of the details of the operation.
Ricke, Zumwinkel and Sommer have denied knowledge of the practice.
Current chief executive Rene Obermann was also quoted by newspapers on Saturday as denying involvement in the spying scandal and pledging to help with investigations.
The telecoms giant insists that the Berlin consultancy firm it hired had not listened to journalists' conversations, but only logged details on who phoned whom as well as the time and duration of the calls.
But the scandal is proving deeply damaging in a country already nervous about "Big Brother" style privacy invasion.