Mercedes-Benz’s diesel cars produced an average of 0.406g/km of NOx on the road, at least 2.2 times more than the official Euro 5 level and five times higher than the Euro 6 level. A spokesman for Mercedes-Benz said: “Since real-world driving conditions do not generally reflect those in the laboratory, the consumption figures may differ from the standardised figures.”

Honda’s diesel cars emitted 0.484g/km of NOx on average, between 2.6 and six times the official levels. A spokesman for Honda said: “Honda tests vehicles in accordance with European legislation.”

Mazda’s diesel cars had average NOx emissions of 0.293g/km in the real world, between 1.6 and 3.6 times the NEDC test levels. One Euro 6 model, the Mazda 6 2.2L 5DR, produced three times the official NOx emissions. A spokesman for Mazda said: “In compliance with the law, Mazda works hard to ensure that every petrol and diesel engine it makes fully complies with the regulations.”

Mitsubishi diesel cars produced an average of 0.274g/km of NOx, between 1.5 and 3.4 higher than in the lab. “The NEDC was never intended to represent real-world driving,” said a spokesman for Mitsubishi.

The Emissions Analytics data seen by the Guardian also found Citroen, VW and Audi NOx emissions to be higher on the road than in the EU lab test.

Well, at least it seems like it's more of a flaw on testing methods than actual indiscretion on the part of the car companies.