Martin Winterkorn has announced his resignation as the chief executive of the Volkswagen Group with immediate effect, the company has announced, in the wake of the scandal about a software cheat in American NOx emissions tests.

The 68-year-old executive, who fought off Ferdinand Piech in a power struggle earlier this year, had been expected to have a fresh contract extension ratified by VW’s supervisory board at the end of this week.

However, a select group of board members – known as the presidium – met in Wolfsburg this morning. The panel comprised interim VW Group chairman Berthold Huber, Lower Saxony prime minister Stephan Weil, Wolfgang Porsche (representative of the VW Group’s largest single shareholder) and two works council officials, Bernd Osterloh and Stephan Wolf.

An official statement from Winterkorn said: "I am clearing the way for a fresh start.

“I am shocked by the events of the past few days. Above all, I am stunned that misconduct on such a scale was possible in the Volkswagen Group.

“As CEO I accept responsibility for the irregularities that have been found in diesel engines and have therefore requested the Supervisory Board to agree on terminating my function as CEO of the Volkswagen Group. I am doing this in the interests of the company even though I am not aware of any wrongdoing on my part.

“Volkswagen needs a fresh start – also in terms of personnel. I am clearing the way for this fresh start with my resignation.

“I have always been driven by my desire to serve this company, especially our customers and employees. Volkswagen has been, is and will always be my life.

“The process of clarification and transparency must continue. This is the only way to win back trust. I am convinced that the Volkswagen Group and its team will overcome this grave crisis.”

The VW Group's interim chairman Berthold Huber said: "Mr Winterkorn has worked hard for VW and we would like to thank him for his efforts over the past 10 years, and also for his willingness to take responsibility in this most difficult of situations.

"To avoid speculation, I would like to say that we will talk about his successor on Friday at the earliest."

More from VW emissions scandal:

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- Vehicle recall likely soon, brands yet to finalise plan

- Matthias Muller announced as new VW Group CEO

- How a university lab helped unearth the VW emissions scandal

- Motherson Sumi denies any impact from VW dieselgate

- Made-In-India cars affected?

- 11m vehicles worldwide could come under scanner