Ferdinand Piëch has resigned suddenly from his position as chairman of the 20-person Supervisory Board of Volkswagen AG.

The shock move follows the Volkswagen Management Board's 17 April endorsement of VAG chief executive Martin Winterkorn. This was in response to an article in a German magazine in which Piëch stated he was "distancing himself" from the firm's CEO. 

The Volkswagen Group issued the following media release earlier on 25 April:

1.
The members of the Executive Committee have unanimously determined that in view of the background of the last weeks the mutual trust necessary ‎for successful cooperation no longer exists.

2.
For this reason Professor Dr. Ferdinand K. Piëch has resigned with immediate effect from his position as chairman of the Supervisory Board and from all his mandates as a Supervisory Board member within the Volkswagen Group. In addition, Ms. Ursula Piëch [his wife] has resigned with immediate effect from all her Supervisory Board mandates within the Volkswagen Group.

3.
The position of  chairman of the Supervisory Board will be temporarily assumed by the  deputy chairman Berthold Huber. Mr. Berthold Huber will chair both the Supervisory Board meeting on May 4 as well as the Annual General Meeting on May 5, 2015.

4.
Under the chair of Mr. Berthold Huber the representatives of shareholders and employees will in close cooperation determine the candidate for the new chairman of the Supervisory Board. The election of the future chairman of the Volkswagen Supervisory Board will follow a proposal made by members of the Supervisory Board representing shareholders.

Volkswagen's release was quickly followed by a short statement from Porsche SE:

Stuttgart, 25 April 2015. Dr. Wolfgang Porsche, chairman of the supervisory board of Porsche Automobil Holding SE, Stuttgart, comments [sic] today’s developments at Volkswagen AG as follows:

“We have full confidence in the board of management of Volkswagen Group and we deeply regret the developments of the last few days. We thank Ferdinand Piëch for his decades of extraordinary and highly successful service to the Volkswagen Group. Our great loyalty to the Volkswagen Group and its 600,000 employees remains unchanged and we assume our responsibility as a principal shareholder.“