The biggest ever class action in the UK begins today (13 October), issuing a call for diesel cars across the industry to be investigated and recalled because of fears they are cheating diesel emissions tests. It is being brought by law firm Leigh Day, with support from parents and campaign groups, including Mums for Lungs, ClientEarth, Asthma + Lung UK, and Rosamund Adoo-Kissi-Debrah. More than 1.8 million motorists are also involved in the legal action. (Words: ClientEarth)

The news comes as YouGov polling appears to show that nearly two thirds (63%) of British adults do not trust car manufacturers to tell the truth about the health and environmental impacts of their cars. Pressure is growing on Government to force car manufacturers to withdraw models which are found to contain illegal “defeat devices”, as polling reports that 69% of adults say it is unacceptable that there may still be cars in the UK with this emissions defeat technology.¹

The three-month trial will decide whether a range of diesel vehicles made by the five lead manufacturers contained defeat devices, designed to alter a vehicle’s performance during test conditions, circumventing the intended emission control levels.

Analysis by the International Council on Clean Transportation, who helped to uncover the original scandal in 2015, and the TRUE Initiative estimated that up to 6.9 million vehicles in the UK have emissions so high as to indicate the likely presence of illegal emissions technology.²

Rosamund Adoo-Kissi-Debrah CBE said:
“The evidence shows that illegal pollution from diesel vehicles has caused thousands of premature deaths in the UK. My daughter Ella’s death was the first in the world to be officially linked to air pollution — but we know she is not the only one.

Car manufacturers have a moral and legal duty to put this scandal right. And the Government needs to step up and phase out diesel vehicles that are still on our streets by 2030. It is morally unacceptable that toxic air is still being pumped out by these vehicles without us knowing. As the Coroner said in Ella’s case ‘if it wasn’t for the illegal levels of air pollution, not only would Ella have not have got asthma in the first place, but she would not have died on that fatal night.’ We owe it to every child growing up now to make sure that the air they breathe is safe so that they will not get sick and they will not continue to die.”

A study by the Centre for Research on Energy and Clean Air reported that excess pollution from diesel vehicles likely to be fitted with illegal defeat devices has already contributed to approximately 16,000 premature deaths and 30,000 new cases of childhood asthma in the UK.³

A group of parents organised by Mums for Lungs will be outside the High Court of Justice in London on Monday in order to demonstrate the level of public concern about Dieselgate (pictures). They will be joined by major charities and campaign groups such as ClientEarth, Asthma + Lung UK and Rosamund Adoo-Kissi-Debrah, whose daughter lost her life to air pollution.

Jemima Hartshorn, the founder of Mums for Lungs said:

“It is shocking that a decade after Dieselgate first broke, families are still breathing dirty air from cars that were clearly exceeding legal emission levels. Every child, every parent, every person has the right to breathe clean air — yet car companies choose profit over people’s health.

This court case is a critical moment for justice and accountability. The government must act now to recall these cars and to stop children getting sick from their fumes.”

Across the EU and UK, it is estimated that 24,000,000 sick days will have been taken as a result of the impacts of illegal diesel defeat devices in vehicles, with an economic impact across the continent of £1.04 trillion (€1.2 trillion).³

In a letter to the Secretary of State for Transport, Mums for Lungs, ClientEarth and Asthma + Lung UK are calling on the UK government to ensure car manufacturers investigate and recall cars.⁴

The groups are also calling to ensure that any costs are paid by the manufacturers and not the vehicle owners. ClientEarth launched a legal complaint against the UK government in 2023 over its failure to use existing powers to investigate the use of illegal defeat devices and require corrective action. However, progress on investigations by the Department for Transport has been slow and the government has yet to put in place the regulations that would enable it to require any recalls. With the outcome of the consumer claim litigation expected next Summer, the government risks being caught unprepared.

Emily Kearsey, lawyer at ClientEarth, said:

“Since the Dieselgate scandal first broke a decade ago, auto manufacturers have faced no real accountability. The British public wants polluters to pay, and finds it unacceptable that there could still be cars on our roads with emissions-cheating devices. Beyond this trial, the government has a key role to play. Where illegal activity is shown, the government needs to enforce recalls – paid for by manufacturers. Otherwise public health will continue paying the price.”

Nick Hopkinson, Medical Director of Asthma + Lung UK, said: “Ten years on from when the Dieselgate scandal first broke, diesel vehicles remain the worst polluters on our roads, emitting tiny toxic particles that penetrate deep into the body, causing and worsening a huge range of lung conditions. This class action represents a chance at justice – the government must hold car giants accountable if illegal activity is found to have taken place, because as this YouGov polling shows the public clearly don’t trust the industry to clean up its own mess.”

Notes

1. YouGov Polling:
   YouGov Client Earth Polling Oct 2025 – Dieselgate – Google Sheets
   (YouGov / Client Earth). All figures, unless otherwise stated, are from YouGov Plc. Total sample size was 2,058 adults. Fieldwork was undertaken between 8th – 9th October 2025. The survey was carried out online. The figures have been weighted and are representative of all GB adults (aged 18+).
2. Health impacts of diesel vehicles suspected of using prohibited defeat devices in the EU and UK – Centre for Research on Energy and Clean Air.
3. TRUE Initiative: New analysis supported by TRUE data finds over €1.2 trillion in health damages in Europe from diesel car emissions.
4. Joint letter to SoS DfT (Dieselgate) October 2025 – Google Docs.