LABOUR demanded yesterday that the government “come clean” on when it became aware of the Volkswagen emissions scandal, claiming its response was “unacceptable.”

Global furore erupted this week after the German car giant admitted that 11 million vehicles had been fitted with software which duped US testers into believing they met environmental standards.

The US Environmental Protection Agency said that almost half a million 2009-15 models featured software that switched the engine to a cleaner mode when undergoing official emissions testing.

Once on the road, however, the cars produce nitrogen oxide pollutants at up to 40 times the legal standard.

Leaked documents this week revealed that countries including Britain, France and Germany lobbied behind the scenes to keep outmoded car tests for carbon emissions.

Shadow transport secretary Lilian Greenwood said: “Ministers must come clean and admit when they were first told about the emissions scandal.

“The International Council on Clean Transportation, the body which helped to expose the problem, warned a year ago that dangerously high levels of nitrogen oxide emissions were not confined to America.”

Transport Secretary Patrick McLoughlin announced yesterday that diesel cars would be re-tested in Britain.

But Ms Greenwood responded: “It is unacceptable that the government waited this long to take action.”

James Thornton, head of environmental organisation ClientEarth, added: “The public must know the full scale of the problem and urgent action must be taken to fix it.”

Volkswagen chief executive Martin Winterkorn resigned over the scandal but insisted he was not aware of “any wrongdoing on my part.”