Volkswagen CEO Resigns in the Wake of an Escalating Emissions Scandal

Volkswagen CEO Martin Winterkorn resigned today, taking responsibility for the German carmaker's rigging of US emissions tests in the biggest scandal in its 78-year history.

"Volkswagen needs a fresh start — also in terms of personnel. I am clearing the way for this fresh start with my resignation," Winterkorn said in a statement.

He said he was shocked by events of the past few days, above all that misconduct on such a massive scale was possible at the company.

A five-member executive committee had grilled Winterkorn, 68, since morning at Volkswagen's headquarters in Wolfsburg, Germany. The company was under huge pressure to take decisive action, with its shares down more than 30 percent in value since the crisis broke, and the bad news still coming.

German prosecutors said on Wednesday they were conducting a preliminary investigation into the manipulation of vehicle emission test results at Volkswagen, while French Energy Minister Segolene Royal said her country would be "extremely severe" if its investigation into the firm found any wrongdoing.

US authorities are planning criminal investigations after discovering that Volkswagen programmed computers in its cars to detect when they were being tested and alter the running of their diesel engines to conceal their true emissions.

German Chancellor Angela Merkel had urged Volkswagen to move "as quickly as possible" to restore confidence in a company held up for generations as a paragon of German engineering prowess.

Earlier on Wednesday, Germany's transport ministry denied that it had known about the technology Volkswagen used to cheat emissions tests despite acknowledging only months ago that it knew of a general gap between "test" and on-road emissions.

Volkswagen has admitted using software to recognize when a car was being checked in a test center, switching the engine to economy mode and injecting chemicals to cut emissions in order to record "test" results below those seen in normal driving conditions.

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The Guardian calculated that if initial figures are correct, the company could be responsible for nearly 1 million tons of extra air pollution every year. Volkswagen has admitted that 11 million of its diesel engine vehicles could have been fitted with a so-called "defeat" device that reduced the amount of nitrous oxide gases released under test conditions.

If so, they could have produced between 237,161 and 948,691 tons of nitrous oxide emissions annually. The longer term effects are likely to be felt most keenly in Europe, where almost half of vehicles on the road are diesel, and Volkswagen has a greater market share than in the US.

Earlier this year, however, members of Germany's Green party challenged the government on the discrepancy between emissions in the test environment and during normal driving.

The transport ministry responded on July 28 that it was aware of the issue and that it was seeking tighter rules. The answer did not, however, recognize any deliberate rigging.

It acknowledged that not enough had been done to address emissions control devices and said it was working on new "technical rules." The introduction of those rules, it added, was being negotiated with the European Union's executive, the European Commission.

A German newspaper, die Welt, said the answer was tantamount to admitting that it knew of the car emissions "tricks" but a spokesman denied this. "There was no knowledge at the Transport Ministry about the use of emissions control technology," he said.