Major Carmakers Face Landmark Trial Over Diesel Emission Fraud

Published: 13 October. The English Chronicle Desk.

A landmark legal battle has begun at the High Court in London against five of the world’s leading car manufacturers — Mercedes-Benz, Ford, Peugeot/Citroën, Renault, and Nissan — accused of manipulating diesel emissions tests in what has become known globally as the “dieselgate” scandal. The case, described by lawyers as the largest class action in English and Welsh legal history, could potentially involve up to 1.6 million car owners who claim to have been misled about the environmental performance of their vehicles.

The allegations assert that these automakers installed software known as “defeat devices” in their vehicles — systems capable of detecting when a car was undergoing emissions testing. Once detected, the software would automatically reduce the engine’s power output, causing the vehicle to emit lower levels of harmful nitrogen oxides than it did under normal driving conditions. This manipulation allowed the vehicles to appear more environmentally friendly in laboratory tests than they actually were on the road.

The High Court will determine whether the mechanisms installed in these diesel vehicles were specifically designed to deceive clean air laws. If found guilty, the verdict could have profound consequences for the global automotive industry and trigger a wave of compensation claims running into billions of pounds.

The five carmakers, all of whom deny the allegations, have been selected as the lead defendants because of the sheer scale and complexity of the case. Depending on the outcome of the current proceedings, at least nine other major automakers are expected to face similar legal actions in the coming years.

The dieselgate controversy first surfaced in 2015 when the United States Environmental Protection Agency (EPA) accused Volkswagen of using defeat devices to cheat emissions tests. The company later admitted to the allegations, sparking international outrage and investigations across Europe and beyond. In 2020, the UK High Court ruled that Volkswagen had breached European Union laws by deploying such devices, prompting the company to settle with 91,000 British motorists for £193 million. Globally, Volkswagen has paid out more than €32 billion (£27.8 billion) in fines, settlements, and compensation related to the scandal — one of the most costly corporate crises in automotive history.

In the current UK case, lawyers representing motorists argue that the alleged deception has not only undermined consumer trust but also endangered public health. They claim that vehicles still operating on the roads continue to emit hazardous levels of nitrogen oxides — pollutants known to contribute to respiratory diseases and environmental degradation.

Martyn Day, a senior partner at Leigh Day — one of 22 law firms representing the affected drivers — said, “A decade after the Dieselgate scandal first came to light, 1.6 million UK motorists now have their chance to establish at trial whether their vehicles contained technology designed to cheat emissions tests.” He added that if the claims are proven true, it “would demonstrate one of the most egregious breaches of corporate trust in modern times,” highlighting that millions of people may have unknowingly inhaled harmful pollutants due to these deceptive practices.

The accused manufacturers, however, continue to reject the allegations. A spokesperson for Mercedes-Benz described the software mechanisms used in their vehicles as “justifiable from a technical and legal standpoint.” Similarly, Renault and Stellantis — the parent company of Peugeot and Citroën — stated that their vehicles were fully compliant with all regulations applicable at the time of sale. Ford called the claims “without merit,” while Nissan reiterated its commitment to compliance in every market where it operates.

Legal analysts suggest that the trial, which is expected to continue well into 2026, could reshape how vehicle emissions are regulated and tested worldwide. A judgment is not anticipated before the summer of 2026, and if the court rules against the manufacturers, a second phase of the trial will be held in the autumn to determine the level of compensation owed to car owners.

For now, the High Court proceedings mark another crucial turning point in the long-running saga that has haunted the automotive industry for nearly a decade — a reckoning that could redefine corporate accountability in an age increasingly defined by environmental responsibility and public trust.