A major legal trial begins this Monday at London’s High Court, confronting five prominent carmakers—Mercedes, Ford, Peugeot/Citroën, Renault, and Nissan—over allegations that they installed software designed to cheat emissions tests.
This case is the largest group claim in English and Welsh legal history, potentially involving over 1.6 million UK vehicle owners. Claimants allege these manufacturers used “defeat devices” in diesel engines that lowered emissions in lab tests but allowed much higher emissions on the road, thus misleading customers about the environmental performance of their cars.
The trial is expected to last around three months, with a final judgment anticipated by summer 2026. If the ruling goes against the carmakers, further hearings on compensation amounts will likely follow in autumn next year.
The outcome could also influence claims against other manufacturers, including BMW, Jaguar Land Rover, Vauxhall, Toyota, and Hyundai-Kia, who face similar allegations.
The dieselgate scandal first broke in 2015 when Volkswagen was caught using prohibited software to cheat U.S. emissions tests. Since then, the scandal has engulfed the global car industry, leading to huge fines and legal settlements. Volkswagen alone has paid over €32 billion worldwide, including a recent £193 million settlement with affected UK drivers.
Lawyers emphasise the public health dangers, citing that the excess nitrogen oxides emitted by these vehicles pose serious risks to millions of people.
“A decade after the Dieselgate scandal first came to light, 1.6 million UK motorists now get their chance to establish at trial whether their vehicles contained technology designed to cheat emissions tests,” said Martin Deigh of Leigh Day, one of the firms representing claimants.
He added that confirming the allegations would reveal “one of the most egregious breaches of corporate trust in modern times,” with millions exposed to harmful pollution unknowingly.
The manufacturers have denied the accusations. Mercedes insists the systems used were “justifiable from a technical and legal standpoint,” while Renault and Stellantis, owner of Peugeot and Citroën, maintain their vehicles complied with regulations in force at the time. Ford calls the claims “without merit,” and Nissan says it is “committed to compliance in all markets we operate in.”
In preparation for the trial, the High Court ordered the release of key internal documents previously withheld by the manufacturers, which are expected to play a crucial role in determining whether the software was designed to deceive emissions testing.