The global “dieselgate” scandal began in 2015 when the US Environmental Protection Agency discovered that Volkswagen Group had installed illegal emissions-cheating software in millions of diesel vehicles.
The software could detect when a vehicle was undergoing emissions testing and temporarily adjust engine performance to produce cleaner results. In normal driving conditions, however, the same vehicles emitted far higher levels of pollution.
The revelations triggered investigations and lawsuits around the world and exposed one of the largest corporate scandals in the automotive industry.
Which car manufacturers have faced dieselgate allegations?
After the Volkswagen scandal emerged, researchers and regulators began examining diesel vehicles produced by other manufacturers.
Investigations suggested that some diesel cars from several brands were emitting levels of nitrogen oxide (NOx) pollution far above legal limits.
Manufacturers linked to diesel emissions litigation or investigations include:
- Volkswagen
- Vauxhall
- Audi
- Porsche
- Daimler AG (the parent company of Mercedes-Benz)
- BMW
- Ford
- Mazda
- Peugeot
- Renault
- Nissan
- Citroën
- Chrysler
- SEAT
- Skoda
The extent of the allegations varies between manufacturers, and not all companies have admitted wrongdoing. Nevertheless, the scale of the allegations has made dieselgate one of the largest consumer disputes ever seen in the automotive sector.
Major UK dieselgate lawsuits
Diesel emissions claims have been brought against multiple manufacturers in the UK. Some cases have already been resolved, while others are still working their way through the courts.
One of the most significant settlements so far came in 2022, when Volkswagen agreed to pay £193 million to settle a group claim brought by more than 90,000 UK vehicle owners.
However, litigation involving other manufacturers continues.
The latest High Court trial
One of the largest ongoing diesel emissions cases in the UK is the Pan-NOx group litigation, which involves more than 1.6 million vehicle owners.
The case concerns diesel vehicles produced between 2012 and 2017 by five manufacturers:
- Mercedes
- Ford
- Peugeot / Citroën
- Renault
- Nissan
Claimants argue that certain vehicles were fitted with prohibited emissions “defeat devices” designed to reduce emissions during laboratory testing while allowing higher pollution levels during normal driving.
The manufacturers deny the allegations.
The trial has already heard 10 weeks of evidence, examining how the vehicles’ emissions systems were designed and whether they complied with EU regulations in force at the time.
In March 2026, the case entered its final phase, with three weeks of closing submissions beginning before Lady Justice Cockerill in the High Court.
Lawyers for vehicle owners described the case as turning on detailed engineering evidence about how emissions control systems operate. The claimants argue that the devices worked exactly as alleged and resulted in significantly higher nitrogen oxide emissions during real-world driving.
Defendants maintain that their vehicles complied with applicable regulations and dispute that any unlawful defeat devices were installed.
Once closing arguments are complete, the judge is expected to reserve judgment, meaning a decision will be delivered at a later date.
Why diesel emissions matter
The dieselgate scandal raised serious concerns about air pollution and public health.
Nitrogen oxide (NOx) emissions contribute to respiratory disease and poor air quality. According to the European Environment Agency, air pollution linked to nitrogen dioxide is associated with tens of thousands of premature deaths in Europe each year.
Research has suggested that millions of diesel vehicles across Europe may emit higher levels of pollution in real-world driving conditions than during laboratory testing.
These findings have triggered regulatory changes, tighter emissions testing rules, and increased scrutiny of vehicle manufacturers.
What does dieselgate mean for UK drivers?
For many drivers, the issue is primarily financial.
Vehicle owners argue that they paid more for cars that were marketed as cleaner and more environmentally compliant than they actually were. Some claim their vehicles also lost value after the scandal emerged.
That has led to large group legal actions seeking compensation from manufacturers. While some cases have already resulted in settlements, others — including the current High Court litigation — could take time to resolve.
How Join the Claim can help
Join the Claim helps raise awareness of major consumer legal actions, including diesel emissions claims. In some cases, we also connect consumers with SRA-regulated law firms that specialise in group litigation.
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.
- Last Updated: April 2026
- Next Update Scheduled: April 2027
