A major trial has begun at London’s High Court, marking a pivotal moment in one of the largest environmental and consumer justice cases in UK history. Five leading carmakers — Mercedes, Ford, Peugeot/Citroën, Renault and Nissan — are accused of cheating on emissions tests, misleading millions of drivers, and contributing to harmful levels of pollution.
The manufacturers deny any wrongdoing, insisting their vehicles complied with the law and were approved by regulators. But if the claims are upheld, this case could potentially pave the way for hundreds of thousands of UK drivers to receive compensation.
The story behind Dieselgate
The Dieselgate scandal began in 2015, when US regulators discovered that Volkswagen had installed software designed to detect when a vehicle was being tested in a laboratory. During testing, emissions were reduced. But when driven normally, those controls were switched off — producing pollution levels far above legal limits.
Volkswagen later admitted to using the software and paid out more than £27 billion in fines and compensation. UK claimants alone received a £193 million settlement in 2022 — around £2,120 per driver.
That case set an important precedent, and investigators across Europe began examining whether other manufacturers had used similar software. Now, the High Court in the UK is testing those allegations against five more major brands.
What’s happening in court
The High Court trial marks the first phase of the UK’s largest-ever collective legal action. Because the overall case involves around 1.6 million drivers and 13 manufacturers, the court selected five “lead defendants” — Mercedes, Ford, Renault, Peugeot/Citroën and Nissan — to represent the broader issues being tested. The lead trial will determine key legal questions, such as whether the technology amounted to “defeat devices”, and whether consumers were misled.
Lawyers argue that these carmakers “chose to cheat rather than comply with the law”. Their submissions rely on expert reports estimating that excess nitrogen oxide (NOx) emissions from diesel engines could have contributed to over 124,000 premature deaths and 98,000 new cases of childhood asthma across Europe between 2009 and 2024.
All five defendants strongly deny the allegations.
- Mercedes says its systems were “technically and legally justified.”
- Ford has described the claims as “scientifically illiterate.”
- Renault, Nissan, and Stellantis (owner of Peugeot and Citroën) also insist that their diesel models met all legal standards when sold.
The trial is expected to run until the end of 2025, with further legal arguments scheduled for early 2026. A final judgment could arrive by summer 2026, though this timeline may shift as proceedings develop.
Whatever the court decides in this initial trial will likely set the direction for the remaining cases involving other manufacturers, whose claims are currently on hold pending the outcome.
Could you be owed compensation?
For years, diesel vehicles were marketed as the cleaner, more efficient choice. Drivers often paid more for models promoted as “low-emission”, only to later discover that those claims may have been misleading. As a result, owners could have overpaid, lost resale value, or unwittingly contributed to pollution.
Courts have already confirmed wrongdoing in similar cases. In 2020, the High Court ruled that Volkswagen had breached European law by using defeat devices, and the company later settled for £193 million, paying an average of £2,120 per claimant. That outcome set a powerful precedent — and now, millions of drivers could follow suit.
Who could be affected?
If you bought, leased, or financed a diesel vehicle between 2009 and 2020, your vehicle could be among those under investigation.
Eligibility varies by manufacturer, model and year, and not every diesel vehicle will qualify. Even if you’ve since sold your car, you may still be eligible, depending on when you owned it and the court’s final definition of who can join the claim.
Taking action: how to join the emissions claim
Drivers don’t need to go it alone. The Dieselgate cases are being pursued through group litigation, which allows people affected by the same issue to come together for a stronger collective case. At Join the Claim, we work with trusted, regulated UK law firms who specialise in these cases.
If you owned or leased a diesel car between 2009 and 2020, you could be owed thousands in compensation per vehicle.
Join the Claim connects consumers with SRA-regulated lawyers. Visit the claim page to check your eligibility if a claim is open with one of our trusted legal partners. If a group action has not yet been launched, you can register your interest and we’ll keep you informed if a partner firm decides to take a claim forward.
