Former VW chief Martin Winterkorn charged

Former Volkswagen chief executive Martin Winterkorn has been charged by US prosecutors for his role in the dieselgate emissions scandal that erupted in 2015.

Winterkorn, 70, has been accused of conspiring to mislead regulators about Volkswagen's efforts to deliberately cheat testing of its diesel-powered vehicles.

Charges were filed against him in March before being revealed from Detroit on Thursday, Reuters reports.

Winterkorn is the ninth person to be hit with US criminal charges connected to the dieselgate saga, and according to US Attorney General Jeff Sessions, is proof the emissions cheating went "all the way to the top".

Volkswagen has declined to comment.

The repercussions of US-based charges against Winterkorn are unknown, given that Germany does not normally extradite its citizens.

The dieselgate scandal broke in September 2015, when the Volkswagen Group – which owns VW, Audi, Skoda, Porsche, Bugatti, Bentley, Lamborghini – was found to have used a cheat device inside its engines to beat laboratory emissions tests.

Winterkorn resigned soon after the scandal broke, but has always maintained that he reported illegal activity to authorities soon after becoming aware of it.

Globally, around 11 million vehicles are affected, which output up to 40 times the NOx (nitrogen oxides) allowed by US law. NOx are harmful to humans. The scandal has already claimed the heads of several executives in Germany and recently saw the jailing of an engineer.

In Australia, roughly 90,000 vehicles have been swept up in the scandal, which is currently subject to ongoing class actions.

The Volkswagen Group has been fined by several countries and has been forced to pay around $14 billion in compensation in the USA alone, after it was fined and forced to buy back around half a million vehicles. US prosecutors have stated that investigations will continue.