The former chief executive of Volkswagen (VW), Martin Winterkorn, has been charged in the US in connection with the emissions scandal.

According to court documents filed in a district court in Detroit, he and a number of other executives are accused of misleading regulators.

Mr Winterkorn, who resigned from the company as a storm erupted over the company's behaviour in September 2015, has always maintained he knew nothing about software designed to cheat lab emission tests.

It emerged then that VW had installed the so-called defeat device in 11 million vehicles worldwide.

It has since cost the company more than US$30bn (€25bn) in fines, fixes and compensation to date - the majority of the sum in the US as its behaviour broke American law.

VW has denied falling foul of rules in the European Union.

A spokesperson for the prosecutor's office in Detroit confirmed Mr Winterkorn was not in custody.

He is also facing a criminal investigation in VW's home country of Germany.

VW has used the fallout from the scandal to place a new emphasis on electric car technology, as diesel power becomes mired by government crackdowns on pollution despite some industry protestations that it has become cleaner than ever.

New rules have since been introduced to ensure all new petrol and diesel-engined cars meet 'on the road' emission limits.