Volkswagen’s top executive in the US, Michael Horn, has left the company almost six months after the emissions scandal came to light in the country.

VW confirmed that Michael Horn was leaving “to pursue other opportunities effective immediately”.

The statement did not give any further information on the decision, which was a surprise given he was a veteran of 25 years at the company and had been president and chief executive of VW’s US operation for only two years.

It was Horn who has had to handle the fallout from its admission in September that 600,000 cars were sold in the US with software designed to cheat emissions tests.

He admitted then that VW had been “dishonest”, adding “we totally screwed up”.

The company is still grappling with regulators over the terms of a fix for the vehicles affected while it also faces further, and potentially more damaging, bills from legal action.

A civil case announced by the US Department of Justice over alleged breaches of environmental law could run alongside investigations by state and federal regulators, while owners of the cars are also massing for class-action suits.

All that is in the US alone.

There are 11 million diesel vehicles affected worldwide.

Top VW officials in Germany, with a nod to the US, warned earlier this week that “unprecedented” fines against the company would be counterproductive as they would likely lead to sweeping job losses.

Mr Horn was the public face of VW in the immediate aftermath of the diesel emissions admission.

He told a US Congressional committee in October: “On behalf of our company, my colleagues in Germany and myself, I would like to offer a sincere apology for Volkswagen’s use of a software programme that served to defeat the regular emissions testing regime,” he said.

“We have broken the trust of our customers, dealerships and employees, as well as the public and regulators.”

Mr Horn said he first learned VW’s diesel cars had issues with dirty emissions in 2014 but insisted he was unaware of the cheating software until a day before the scheme was publicly revealed in September.

It was announced this week in Germany that 17 people are being investigated – up from an initial six.

French prosecutors also launched a formal investigation into suspected “aggravated fraud” by the company.