On average, the cars emit seven times the permitted level of NOx gasses, with the worst car producing 22 times the legal limit. Models from every major motor manufacturer breached the limit when they were evaluated in real-world conditions.

From 1 September, new diesel cars in the EU have had to comply with emissions rules called “Euro 6”. However, carmakers can use a whole range of techniques to ensure that their cars perform far better under test conditions than when driven by ordinary drivers.

These include stripping components from the car to reduce weight, using special lubricants, over-inflating tyres and using super-smooth test tracks. The same techniques are used to boost the apparent fuel efficiency of vehicles.

The report, from sustainable transport group Transport & Environment (T&E), compiled recent data to show that when diesel vehicles are tested in normal driving conditions they emit much greater levels of NOx gases. NOx gases and other vehicle-related pollution are estimated to cause half a million premature deaths each year in the EU.

The T&E report also found that motor manufacturers often sell less polluting models of the same cars in the US, where emissions rules are stricter. This is achieved by including devices that capture pollution and cost a few hundred euros.

“Every new diesel car should now be clean but just one in 10 actually is,” said Greg Archer, T&E’s clean vehicles manager. “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.”

In April, the UK’s supreme court ordered the government to tackle the UK’s air pollution, which has been in breach of EU limits for years. Proposals from ministers released on Saturdayinclude improving public transport and creating low-emission zones in a number of cities, perhaps following the lead of central London where most diesel drivers will have to pay a £12.50 pollution charge from 2020.

There are plans to introduce a new on-road test that will measure the real-world emissions of diesel cars, but it will not apply to all new EU cars until 2018 at the earliest. Carmakers have argued that on-road testing should be delayed until 2020.

“We cannot choose where we breathe so we must stop cars polluting our city air,” concludes the T&E report. “The technology to clean up vehicle exhausts is available and costs a few hundred euros. It is a small price compared to the nearly €1tn spent annually in health care and lost output and productivity. Cars with engines must be stopped from polluting our air or prevented from accessing our cities.”

Damian Carrington, the guardian 

This article first appeared on the guardian 

Edie is part of the Guardian Environment Network

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