Martin Winterkorn, who stepped down as the CEO of Volkswagen last week, remains in a top executive position at Porsche Automobil Holding, the holding company which controls just over 50% of Volkswagen’s shares, Bloomberg reports this morning.

German prosecutors opened an investigation yesterday to examine the role that Winterkorn played in the emissions-rigging scandal.

Other senior executives at Volkswagen will also be investigated as German authorities aim to determine who was responsible for the company's cheating in emission tests. Executives at the company could face fraud charges.

He also remains chairman of the group’s separate, publicly-quoted Audi division and of the group’s truck holding company.

Some leading representatives of the powerful IG Metall trade union are questioning his continuing role in the group and any potential major severance deal which he might enjoy.

Under his contract, Winterkorn might be entitled to a pay-out of twice his annual remuneration, which was close to €16m last year.