Carried out by environmental campaign group T&E for its new report, Don’t Breathe Here, the research suggests that every major car manufacturer is selling diesel cars that fail to meet EU air pollution limits on the road in Europe. On average new EU diesel cars produce emissions about five times higher than the allowed limit, the research found, whilst the worst car was found to emit 22 times the limit.

The organisation blamed Europe’s testing system, which it said is obsolete, allowing carmakers to use cheaper, less effective exhaust treatment systems in cars sold in Europe, according to newly released data. In contrast, diesel cars sold by the same manufacturers in the US, where limits are tighter and tests are more rigorous, were found to have better exhaust treatment systems and produce lower emissions. ​A new on-road test will, for the first time, measure diesels’ ‘real-world’ emissions but it will not apply to all new cars until 2018 at the earliest.

Greg Archer, T&E’s clean vehicles manager, said: “Every new diesel car should now be clean but just one in 10 actually is. This is the main cause of the air pollution crisis affecting cities. Carmakers sell clean diesels in the US, and testing should require manufacturers to sell them in Europe too."

It added that the cost to manufacturers of a modern diesel after-treatment system is around €300 per car.