Five Global Carmakers Face Trial in London Over Alleged Emissions Cheating

A major class-action lawsuit has opened at the High Court in London against five of the world’s leading car manufacturers accused of using illegal software to cheat emissions tests.

The companies – Mercedes, Ford, Peugeot/Citroën, Renault, and Nissan – are alleged to have installed “defeat devices” that made their vehicles appear more environmentally friendly during official testing than they were in real-world driving conditions. All five manufacturers have denied the allegations.

The case, which lawyers say could become the largest class action in UK legal history, involves claims from around 880,000 car owners, and could ultimately expand to 1.6 million motorists.

Opening arguments on Monday saw Thomas De La Mare KC, representing the claimants, accuse the carmakers of prioritising profits over public health. “Each player in the industry basically took a conscious decision that customer convenience, which helped the industry sell more cars, was more important than preventing pollution,” he told the court.

De La Mare cited research from the Centre for Research on Energy and Clean Air, which estimated that excess nitrogen oxide emissions from diesel vehicles had caused 124,000 premature deaths and 98,000 new cases of childhood asthma across the UK and Europe between 2009 and 2024.

However, the defendants strongly rejected any wrongdoing. Renault’s counsel, Alexander Antelme KC, described the accusations as “without merit and untenable,” arguing that the challenged features were “appropriate and necessary elements of a well-designed diesel engine.”

Ford’s lawyer, Neil Moody KC, went further, calling the lawsuit “scientifically illiterate” and “flawed on the facts and the law,” adding that the suggestion of an industry-wide conspiracy was “implausible.”

The case stems from the 2015 ‘Dieselgate’ scandal, when the US Environmental Protection Agency discovered that Volkswagen had used software to manipulate emissions results. Volkswagen later admitted to installing such devices in 11 million vehicles worldwide and paid more than £26 billion in fines and settlements.

Following that revelation, other manufacturers have faced scrutiny over similar claims. In 2020, the UK High Court ruled that Volkswagen had indeed breached EU emissions laws and later reached a £193 million settlement with 91,000 British drivers.

Outside the High Court on Monday, campaign group Mums for Lungs and clean air advocate Rosamund Adoo-Kissi-Debrah, whose daughter Ella became the first person in the UK to have air pollution listed as a cause of death, gathered to show support for affected motorists.

All the accused carmakers have maintained that their vehicles complied with regulations at the time of sale. Mercedes said its systems were “justifiable from a technical and legal standpoint,” while Renault and Stellantis (the parent company of Peugeot and Citroën) insisted their cars met all legal standards. Ford and Nissan also described the claims as “without merit.”

The trial, overseen by Lady Justice Cockerill, is expected to continue through December 2025, with legal arguments resuming in March 2026 and a final judgment anticipated in summer 2026.