Volkswagen US chief admits he knew cars flouted emission rules

Michael Horn offers 'sincere apology' ahead of Congressional hearing over Volkswagen's use of software to cheat pollution tests

Volkswagen's US chief said he knew more than a year ago that the group's cars possibly breached pollution rules, as he prepared to apologide today before Congress over the massive scandal.

In testimony released ahead of his hearing before a Congressional committee, Michael Horn offered a "sincere apology" over Volkswagen's use of a software designed to cheat pollution tests.

The German auto giant has sunk into the deepest crisis of its history after revealing that it equipped 11 million of its vehicles worldwide with software that switches the engine to a low-emissions mode during tests.

The so-called defeat devices then turn off pollution controls when the vehicle is on the road, allowing it to spew out harmful levels of toxic gases.

The shocking revelations have wiped more than 40 percent off Volkswagen's market capitalization, but the direct and indirect costs are still incalculable as the company risks fines in several countries and possible damages from customers' lawsuits.

Horn said he learnt in early 2014 of "a possible emissions non-compliance", after researchers at the University of West Virginia found that VW cars it tested were releasing up to 40 times as much nitrogen oxide as was legally permissible.

He said he was told by his staff then that US authorities could conduct tests for so-called "defeat devices", which switches the car to a low emissions mode when cars are undergoing tests.

The US boss for Volkswagen said he was informed later that year that technical teams had a plan to bring the vehicles into compliance, and that they were working with the authorities on the process.

Volkswagen finally admitted to US regulators in September this year that hidden software installed in certain diesel vehicles "could recognize whether a vehicle was being operated in a test laboratory or on the road," Horn said.

Admitting that the company had "broken the trust of our customers, dealerships, and employees, as well as the public and regulators," Horn vowed to hold those responsible accountable.

Separately, VW Korea President Thomas Kuehl was also due to be grilled in the South Korean parliament Thursday afternoon, according to state broadcaster KBS.