Gerhard Schäfer, 70, the former head of Germany’s highest court, will “examine all relevant data security aspects of the allegations and draw up a new data security plan for the group,” Deutsche Telekom said in a statement.

Deutsche Telekom was forced to concede at the weekend that it had hired an outside firm to track hundreds of thousands of phone calls by senior executives and journalists to identify the sources of press leaks.

The Bonn-based company said the “ill-advised use of communications data” happened in 2005 and probably 2006 and has to date conceded only to spying on the magazine Capital. But on Thursday the Financial Times Deutschland alleged that it was also spied on and that there was even a secret camera installed in its newsroom.

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 and chief executive Rene Obermann has embarked on a damage control campaign. Prosecutors raided the firm’s Bonn headquarters on Thursday.

Earlier this year it emerged that discount food retailer Lidl had hired detectives to install micro cameras that filmed employees while at work and on their breaks. Lidl recorded employees when they used the toilet, their conversations while on break and kept track of who their friends outside work were.