Millions of drivers lose initial ‘Dieselgate 2’ High Court battle: Judge rules carmakers broadly did not use emissions-cheating devices

Some of the world’s biggest carmakers on Friday won overall the first stage of Britain’s biggest class action legal battle over whether some of their diesel vehicles use ‘prohibited defeat devices’ (PDDs).

More than a dozen manufacturers have been accused by 1.6 million British motorists of using devices to cheat official emissions tests on diesel models produced from 2009.

The vehicles in the claims were produced by Mercedes-Benz, Opel and Vauxhall, Nissan and Renault, Volkswagen and Porsche, Peugeot and Citroën, Jaguar Land Rover, Ford, BMW, FCA and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda.

During the 13-week trial, which began in October, evidence was presented against 20 sample vehicles produced by five manufacturers (Mercedes-Benz, Renault, Nissan, Ford, Peugeot and Citroën); Other manufacturers were also committed to today’s decision.

Drivers’ lawyers told the hearing that devices installed in cars allow them to detect when vehicles are being tested and comply with emissions regulations by changing the amount of harmful emissions produced.

They argued that this allowed vehicles to pass emissions tests when actual outputs were much higher, which meant the vehicles were in breach of regulations and therefore a breach of contract.

In a 369-page judgment published on Friday afternoon, Lady Justice Cockerill said most of the strategies did not constitute PDD, except one used on Mercedes cars and some Peugeot-Citroën vehicles, which were removed in 2015.

He said that ‘many of the alleged PUDs were not successful’ and that ‘the scope of the claim was much reduced’ as a result of his findings.

For Ford, Renault and Nissan, the judge ruled that defeat devices did not meet the definition of PDD and therefore did not breach emissions regulations.

Leigh Day Solicitors, one of the law firms representing 1.6 million drivers, said the decision created a ‘significant difference between the legal situation in Great Britain and much of Europe’.

All five vehicle manufacturers disputed the allegations at the hearing, saying the vehicles’ strategies to control emissions were appropriate.

Nissan’s lawyers described the case as ‘fundamentally misunderstood’, while Renault’s lawyers said the plaintiffs were ‘pursuing PDD’.

The case follows the Supreme Court’s ruling in 2020 that Volkswagen installed illegal ‘defeat devices’ in thousands of its vehicles in a case known as ‘Dieselgate’.

Mrs Justice Cockerill said there was “no suggestion” that any of the sample vehicles contained a PDD identical to that used by Volkswagen, meaning “any notion that the answer to this case is obvious must therefore be absolutely set aside”.

Martyn Day, senior partner at Leigh Day, who represented the plaintiffs, said: ‘The High Court found that other manufacturers were also using VW-style defeat devices, despite their denials.

‘The judge also found that many other defeat devices were legal because he surprisingly went against established EU jurisprudence on what constitutes a defeat device.

‘If the decision is followed in Great Britain, it will now be the only major place in Europe where manufacturers can produce and sell cars containing such devices.

‘We welcome some of the judge’s findings, but we think significant parts of the decision are disappointing, particularly because of the impact on the environment and consumer protection.’

Lawyers representing the vehicle owners are now considering whether to ask for permission to appeal the decision.

Those taking legal action have either bought, leased or otherwise acquired a vehicle manufactured by one of the companies, most of which are based in England and Wales.

If successful, the class action was believed to be worth at least £6bn.

The campaigner is pictured protesting outside the Royal Courts of Justice in central London on October 13, 2025, as the largest class trial in British history gets underway

Campaign group Mothers for Lungs described the legal decision as ‘bizarre’ and ‘sometimes contradictory’.

A statement on Friday said: ‘The court took a very narrow definition of a diesel defeat device and said in its judgment: ‘If an alternative approach to the meaning of ‘defeat device’ was taken, a greater number of defeat devices would be created, including devices in each of the leading manufacturers’ cars.’

The case focuses on harmful nitrogen oxide (NOx) emissions controlled by an emissions control system.

Thomas De La Mare KC, who filed the lawsuit in October last year, said on behalf of the plaintiffs that the manufacturers would ‘rather cheat than comply with the law’.

Alexander Antelme KC, on behalf of Renault, said in written submissions that the legal action was based on the ‘incorrect assumption that the features of VW Dieselgate apply to the entire automotive industry’.

BMW (238,454), Vauxhall (193,951), Ford (175,244) and Renault/Nissan (148,893) make up the five manufacturers facing the largest number of plaintiffs in the class action.

Another hearing regarding the claim is expected to be held in October.