Police are investigating whether eavesdroppers were listening in to Wendelin Wiedeking in a hotel room on the eve of a supervisory board meeting in Wolfsburg last September.

A switched-on baby monitor was found behind a sofa in the room where Wiedeking was staying, reported Spiegel magazine.

Porsche's own security firm found the monitor but state prosecutors from the local city of Braunschweig are now taking over the case, the magazine added.

According to a separate report in Focus magazine, Porsche has also complained to the police that the phone of the chief of its works council Uwe Hueck, was tapped.

Porsche, Volkswagen's largest shareholder and due to take a majority shareholding by later this year, is currently in dispute with the Volkswagen works council over co-determination rights. It is also disputing with Volkswagen's second largest shareholder, the State of Lower Saxony, over its right of veto in major decision-making.