Volkswagen has announced that Michael Horn, chief executive and president of the company's US business, is stepping down with immediate effect.
Horn is leaving "to pursue other opportunities", the group said. He will be replaced on an interim basis by Hinrich J. Woebcken, recently appointed head of the north American region and chairman of Volkswagen Group of America.
Volkswagen has endured a rocky six months, since it was revealed that the car maker had fitted millions of diesel vehicles with technology allowing them to cheat emissions tests.
In October last year, Horn admitted he was made aware of “possible emissions non-compliance” by the company in 2014.
He made the revelation during a testimony to investigators at the House of Representatives.
"I was informed that EPA regulations included various penalties for non-compliance with the emissions standards and that the agencies can conduct engineering tests which could include 'defeat device' testing or analysis,” he said.
VW chief executive Martin Winterkorn resigned days after the scandal erupted last September and said he accepted responsibility for the "irregularities" found in diesel engines.
An estimated 11m cars worldwide were fitted with the so-called "defeat devices".