Renault and Nissan have been accused of emissions cheating by law firm Harcus Parker, which claims that up to 1.3 million cars could be fitted with a ‘defeat’ device.
Both manufacturers strongly deny the allegations.
London-based Harcus Parker says it has seen independent test data that suggests 700,000 Renaults and 600,000 Nissans in the UK made between 2009 and 2018 could be affected.
It includes around 100,000 1.2-litre petrol versions of the Qashqai, plus diesel-powered Note, Juke and X-Trail. Diesel versions of Renault’s Clio, Espace, Captur, Megane and Scenic are all named in the allegations too.
The allegations follow those recently made against Mercedes-Benz, which has co-developed come powertrains with the Renault Nissan Alliance.
Damon Parker, senior partner at Harcus Parker, said: “For the first time, we have seen evidence that car manufacturers may be cheating emissions tests of petrol, as well as diesel vehicles.
“We have written to Renault and Nissan to seek an explanation for these extraordinary results, but the data suggests to me that these vehicles, much like some VWs and Mercedes cars, know when they are being tested and are on their best behaviour then and only then.
“These are vehicles which could and should meet European air quality limits in normal use, but rather than spend a little more on research and development, Renault and Nissan appear to have gone down the same path as VW and Mercedes and decided to cheat the tests.”
The law firm says owners of the affected vehicles could be due up to £5,000 in compensation if the claim is successful.
Nissan said: "Nissan strongly refutes these claims. Nissan has not and does not employ defeat devices in any of the cars that we make, and all Nissan vehicles fully comply with applicable emissions legislation.”
Renault said: "All Renault vehicles are, and always have been, type-approved in accordance with the laws and regulations for all the countries in which they are sold and are not fitted with ‘defeat devices’.”