VW Group is not the only manufacturer facing questions around emissions. Renault and Fiat are now strenuously denying claims made against them over emissions in France and the US respectively.

Claims were made against Renault in France after independent tests showed higher NOx emissions in real-world driving compared to the official figures.

The initial investigation ended last November, but has now been taken up by the public prosecutor in Paris, which has inter-regional jurisdiction in consumer affairs in France.

The French Government will allow the courts to decide if further action is needed. A statement from Renault said: “Renault complies with French and European regulations. Our vehicles all are and have always been homologated in accordance with the laws and regulations. They are compliant with the applicable standards and are not equipped with cheating software affecting anti-pollution systems.”

Meanwhile, the American Environmental Protection Agency (EPA) has issued a ‘notice of violation’ against Fiat Chrysler Automobiles (FCA) claiming it failed to notify the organisation that one of its diesel engines was fitted with software which affects NOx emissions. The software used is not illegal in the   US but the EPA says FCA should have disclosed the software.

A spokesperson for FCA UK said: “The US and the EU are completely different markets, with different software calibrations, standards, testing and homologation processes. FCA vehicles sold in the EU conform to EU emission regulations.”

Nick Molden, Emissions Analytics (EA) founder and chief executive, has been testing NOx emissions in the UK from 39 manufacturers.

The average across all manufacturers EA tested shows vehicles performed at 5.1 times over the limit for NOx. The legal limit is 80mg/km NOx.

EA rates cars from ‘A’ – meets Euro 6 Nox limit for diesel and Euro 4 limit for petrol – to ‘H’ – roughly equal to more than 12 times the Euro 6 limit. The Renault Espace 1.6 diesel and the Megane 1.5 diesel (both automatics) received an H rating, as did the Fiat 500X 1.6 diesel. The Infiniti Q50 2.1 diesel (auto) and Subaru Outback 2.0 diesel (auto) were among other models to receive an H rating.

EA tested four Fiat diesels – one Euro 5 and three Euro 6. On average, the diesels showed 9.4 times the limit for the level of NOx emissions. It also tested six Renault engines – two Euro 5 and four Euro 6. The results showed an average of 13.4 times the limit for NOx emissions.

A Renault spokesman said: “It is normal to find differences between laboratory testing and the results obtained with on-road use.”

Fiat declined to comment on EA’s results.                                                      

Molden said discrepancies between the real world and the test conditions that give the official figures can be expected due to the “overly gentle official NEDC cycle”. However, he thought two times over the legal limit was a reasonable discrepancy.