Car makers have decided they would rather cheat by prioritizing “customer convenience” and sell cars than comply with the law on deadly pollutants, the first day of the biggest class-action trial in English legal history has emerged.
More than a decade after the original “dieselgate” scandal broke, lawyers representing 1.6 million diesel car owners in the UK argue that manufacturers intentionally installed software to falsify emissions tests.
They claim that “prohibited defeat devices” could detect when cars were under test conditions and ensure that harmful NOx emissions were kept within legal limits, deceiving regulators and drivers.
If the claim is successful, the estimated damage could exceed £6 billion. The three-month hearing, which opened at London's high court on Monday, will focus on vehicles sold by five manufacturers – Mercedes, Ford, Renault, Nissan and Peugeot/Citroën – since 2009. In “real world” road conditions, lawyers argue, cars produce much higher levels of emissions.
The decision on the five main defendants will also be binding on other manufacturers, including Jaguar Land Rover, Vauxhall/Opel, Volkswagen/Porsche, BMW, FCA/Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda, whose cases are not being considered, in order to reduce the time of trial and costs.
Opening the plaintiffs' case, Thomas de la Mare K.S. said, “Every player in the industry has essentially made a conscious decision that customer convenience, which has helped the industry sell more cars, is more important than reducing emissions of deadly pollutants.”
In written submissions, the claimants cited a report from the Center for Energy and Clean Air Research which found that excessive NOx emissions were responsible for 124,000 premature deaths in the UK and Europe between 2009 and 2024.
De la Mare told the high court that emissions levels could be easily reduced if cars had larger tanks for AdBlue – an additive that reduces NOx emissions in diesel cars – and asked customers to fill them up. Instead, he said: “They basically said that the concern about getting these cars to be sold at the expense of eliminating these inconveniences is so strong… that we would rather cheat than comply with the law.”
Lead counsel also told the judge, Justice Cockerill, that the producers were trying to argue that numerous previous decisions on Dieselgate abroad, including in US and European courts, did not apply to the UK. He said: “Our position generally is that we will rely on the decisions of foreign regulators rather than on the opinion of the law.”
He said the defendants' arguments meant that “mainland Britain is becoming something of a weapon for the defeat of Brexit Island… But Northern Ireland is applying case law that you are being asked to throw in the bin.”
Documents from Ford's 2010 internal training and briefing on suppression devices showed that “manufacturers could and did understand the law just as we do now,” De la Mare said.
Lawyers for the defendants will make opening statements later this week. Car manufacturers deny using prohibited defeat devices.
In written statements, Renault's lawyers said the case was “riddled with errors and misunderstandings, particularly regarding the design and operation of vehicle emissions control systems,” while Ford representatives said it was “scientifically illiterate.”
Mercedes said the plaintiffs' case is “obsessively focused” on NOx pollution rather than other emissions and does not “recognize the complexity” of diesel technology. Nissan's lawyers said the underlying legal premise of the case was an “unjustifiably broad interpretation of the mechanism of injury.”
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The main evidentiary trial is expected to conclude before Christmas, with a break before legal arguments are heard in March 2026. A decision is expected next summer, followed by a new lawsuit over possible compensation.
Adam Kamenetzky, from south London, the lead plaintiff among 1.6 million owners, told the Guardian outside court: “This is the first time, particularly in the UK, if not in any jurisdiction, that the evidence has actually been made public.
“If these allegations are true, consumers have been deceived at the point of sale and action must be taken to prevent this type of deception from being introduced into vehicles.”
Clean air campaigners, including Mums for Lungs and Rosamund Adu-Kissi-Debra, whose daughter Ella's death was the first officially linked to air pollution, demonstrated outside the court.
Adu-Kissi-Debrah said “illegal pollution from diesel vehicles has caused thousands of premature deaths in the UK”, adding that she hoped for a “day of reckoning” for the use of the fuel.
The landmark claims were brought by more than 20 law firms, led by Leigh Day and Post Goodhead. Leigh Day senior partner Martin Day said the allegations, “if proven, would demonstrate one of the most egregious breaches of corporate trust in modern times.”
Alicia Alinia, chief executive of Pogust Goodhead, said the case would go to “the heart of corporate responsibility and environmental justice.”
