Major car companies chose to ‘cheat’ rather than ‘follow the law’ over emissions, court told
The High Court has heard car manufacturers choose to “cheat rather than comply with the law” on vehicle emissions.
Nearly 1.6 million motorists are taking legal action against more than a dozen manufacturers over allegations that many diesel vehicles produced since 2009 contain “prohibited defeat devices” (PDDs).
This is the largest legal action of its kind in British history.
Driver advocates argue that devices installed in cars allow vehicles to detect when they are being tested and comply with emissions regulations by changing the amount of harmful emissions produced.
This allowed vehicles to pass emissions tests when actual outputs were much higher; A trial in London said the vehicles breached regulations and therefore amounted to a breach of contract.
The case follows the Supreme Court’s ruling in 2020 that Volkswagen installed illegal “defeat devices” in thousands of its diesel vehicles in a case known as “Dieselgate”.
Vehicles in the current claims were produced by Mercedes-Benz, Opel and Vauxhall, Nissan and Renault, Volkswagen and Porsche, Peugeot and Citroen, Jaguar Land Rover, Ford, BMW, FCA and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda.
The cases against 20 “model vehicles” produced by five manufacturers – Mercedes-Benz, Renault, Nissan, Ford, Peugeot and Citroen – are being heard in a three-month trial that began on Monday.
Manufacturers resist the claims and deny that their cars are fitted with PDD; Nissan’s lawyers describe the case as “fundamentally misunderstood” and Renault’s lawyers say the plaintiffs are “PDD hunting”.
Thomas De La Mare KC, who brought the case, said on behalf of the plaintiffs: “What really matters is the industry approach to calibration and technology selection over a long period of time.”
He said that “every player in the industry has made a conscious decision that customer convenience, which helps the industry sell more cars, is more important than preventing pollution.”
He said: “They basically said that the concern to make these cars salable by eliminating these drawbacks is so strong, so valuable, such an important decision or fact in any consumer’s decision about whether or not to buy the car, that we would rather cheat than obey the law.”
He continued: “The law supports our cause at every turn, and this is because the defendants did not comply with the law.”
In his written submissions, the lawyer also said the manufacturers put forward “numerous improbable, even fanciful, legal arguments” about whether PDDs were present in the sample vehicles.
Those currently taking legal action have either bought, leased or otherwise acquired a diesel vehicle manufactured by one of the companies, most of which are based in England and Wales.
Other manufacturers involved in the allegations will be bound by the decision made following the hearing.
In July last year, barrister Benjamin Williams KC told the hearing the trial could be worth at least £6bn.
The case focuses on harmful nitrogen oxide (NOx) emissions controlled by an emissions control system.
In written submissions, Mr De La Mare said a May 2025 report from the Center for Research on Energy and Clean Air found that excess NOx emissions caused 124,000 premature deaths in children and 98,000 new cases of asthma in the UK and Europe between 2009 and 2024.
But Alexander Antelme KC, for Renault, said in written hearing submissions that the legal action was based on the “incorrect assumption that the features of ‘VW Dieselgate’ apply to the entire automotive industry.”
He said: “Renault’s key sample vehicles do not contain override devices or prohibited fault devices, either accidentally or, as the claimants claim, deliberately intended to ‘cheat’ emissions regulations.
“The second claim is unfounded and untenable.”
He continued: “Plaintiffs’ case is riddled with errors and misunderstandings, particularly regarding the design and operation of the vehicles’ emission control systems.”
He added: “The features that plaintiffs mistakenly object to are actually proper and necessary elements of a well-designed diesel engine.”
Neil Moody KC, for Ford, said in written submissions that the case was “scientifically illiterate” and “unfactually and unlawfully”.
He said: “Their case is not only that these vehicles have been designed and marketed in a way that breaches emissions regulation, but as a result of deception and fraud by all manufacturers these vehicles all appear to contain PDD.
“The inference appears to be some sort of industry-wide conspiracy. It only needs to be stated for the proposal to be deemed unreasonable.”
The main hearing before Lady Justice Cockerill will conclude in December, but legal arguments will not be heard until March 2026.
A decision is expected next summer, with a new hearing to determine compensation scheduled for the fall of next year.
