Matthias Müller, the Volkswagen chief executive, is facing possible criminal charges over the 'dieselgate' emissions rigging scandal.

German prosecutors on Wednesday confirmed for the first time that he is under formal investigation in connection with the case.

Mr Müller, who took over at VW in the wake of the 2015 scandal, was supposed to be a clean pair of hands following the resignation of Martin Winterkorn, who took responsibility for the emissions rigging.

But in a serious blow to VW’s attempts to move on from the affair, prosecutors in Stuttgart announced that Mr Müller is being investigated on suspicion of a cover-up.

He is alleged to have withheld information from shareholders about emissions rigging at the company in order to manipulate its share price.

Mr Müller was CEO of VW subsidiary Porsche at the time — as well as a board member at Porsche Holding SE, the VW group’s majority shareholder.