Ditch Diesel

What’s the problem with diesel?

Diesel vehicles emit large amounts of toxic gases, which inflame lungs and make childhood asthma and respiratory problems worse. These gases are called nitrogen oxides (NOx) and nitrogen dioxide (NO2).

The short-term effects of exposure to NO2 include inflammation of the lungs and airways, and long-term exposure can affect lung function and breathing and worsen asthma.

Children are developing lifelong, chronic conditions, including poorly developed lungs, asthma, high blood pressure, inattention and hyperactivity, and mental illness as a result of exposure to air pollution.

How much air pollution do diesel vehicles create?

*Image from the Chief Medical Officer’s air pollution report*

Diesel vehicles are the single biggest contributor to the NOx on our roads, as shown here in this graphic from Chief Medical Officer Professor Chris Whitty’s Air Pollution Report (Figure 6, Page 8).

On average in the UK in 2023, 68 per cent of the NO2 concentrations at the roadside were estimated to have originated as NOx emissions from road transport.

Reducing the number of diesel vehicles on our roads would significantly clean up the dirty air we’re breathing.

Our diesel campaign calls for:

Commitments from all levels of government to phase out diesel by 2030

A manufacturer recall of all diesel cars that are found to have defeat devices installed
A major UK fund, put together by car manufacturers, worth at least £1 billion, to support the phasing out of diesel

Find out about the 2025 Dieselgate class action

Dieselgate and real-world diesel emissions

*Image from the TRUE Initiative article on* *the number of European vehicles emitting “suspicious” or “extreme” emissions*.

The 2015 Dieselgate scandal revealed that defeat devices were likely fitted to diesel vehicles to artificially reduce emissions to pass EU tests. Government agencies across Europe subsequently began to test real-world emissions and discovered that diesel cars across manufacturers emit higher levels of NOx during real-world operation than in laboratory testing.

The International Council on Clean Transportation’s 2017 white paper revealed that some Euro 6 diesel cars (those that are allowed within London’s Ultra Low Emission Zone) were found to exceed the legal limit of 80 mg/km NOx by a factor of 12. The Real Urban Emissions (TRUE) Initiative has given nearly all diesel vehicles on European roads a “poor” rating.

A subseqent 2023 reassessment of excess NOx in diesel cars in Europe revealed that “suspicious” levels of NOx emissions were found in 77 per cent to 100 per cent of tests and vehicle averages, indicating the likely use of a prohibited defeat device.

This led environmental law charity Client Earth to send a legal complaint to the UK Government, demanding they address the legacy of Dieselgate. As a result, the Department for Transport is undertaking an investigation into prohibited defeat devices in 47 types of diesel cars, but no action has yet been taken.

Mums for Lungs’ research on excess diesel emissions

In March 2025 Mums for Lungs commissioned research that revealed that 7.5 million of the UK's 10.7 million diesel cars are Euro 5 and 6 models, emitting 51,400 tonnes of excess NOx annually above legal emission limits (as of June 2024). It was Euro 5 and 6 diesel vehicles that were shown during the Dieselgate scandal to be using defeat devices to pass emissions tests.

Those 7.5 million diesel cars make up just under a quarter of the cars on UK roads, yet their excess emissions are responsible for almost 30 per cent of the total NOx emissions from road transport, including those from vans, buses and HGVs.

When considering Euro 3 and 4 diesel models as well, the cumulative Euro 3-6 excess emissions make up almost 40 per cent of the total NOx emissions from road transport in the UK. This is far higher than previously thought.

Collectively, the 10.7 million diesel cars account for 52.2% of ALL NOx emissions from road transport in the UK.

Health effects of excess diesel emissions

Between 2009 and 2024, excess diesel emissions caused a staggering estimated 16,000 premature deaths, 30,000 cases of asthma in children and 800,000 days of sick leave in the UK, according to a report by the Centre for Research on Energy and Clean Air.

This is why we urgently need national and local governments to phase out diesel from our roads.

The legacy of Dieselgate - 2025 class action

The biggest group claim ever to come before any of the UK courts, representing more than 1.6 million vehicle owners, began in the High Court in October 2025. The details of the case were at first to be deemed confidential due to the commercial interests of the defendants, the car manufacturers.

*Jemima Hartshorn outside the Royal Courts of Justice. Image: Crispin Hughes*

In March 2025, Mums for Lungs wrote an open letter to the judge in the case, calling for documents related to the litigation to be made publicly available due to the significant public interest in this matter. The letter was signed by over 650 individuals, MPs and over 50 charities and campaign groups. We subsequently gathered outside the Royal Courts of Justice to highlight the need for open justice.

In June 2025, we made an application to the Court, as did the environmental law organisation Client Earth. Our application asked the Court to remove the redactions from legal documents filed by car manufacturers and to make the unredacted documents available to third parties on public interest grounds. We attended the Pan-NOx Emissions Group Litigation hearing as a third party at the High Court in July - you can read about this here.

In July 2025, we were delighted to hear that the High Court granted our application in full, and ordered car manufacturers to release unredacted documents ahead of the October trial.

On the first day of the trial, we again gathered outside the Royal Courts of Justice, and wrote to the Secretary of State for Transport with Client Earth and Asthma and Lung UK to call on the government to ensure car manufacturers investigate and recall cars.

A judgment is expected in Summer 2026 and if the car manufacturers are found to have fitted defeat devices, we need to see them held accountable, and immediate action to remove these vehicles from our roads.

Taking action - how to phase out diesel vehicles

National government can fast-track the phase-out of diesel vehicles by:

Using legislation to issue a manufacturer recall of all diesel cars that are found to have defeat devices installed.
Establishing a major UK fund worth at least £1 billion, put together by car manufacturers, to support a phase out.
Providing incentives to encourage the purchase of electric vehicles.
Funding more infrastructure to enable people to switch to active travel options on a larger scale.

Local authorities can:

Set a vision and publicly commit to a diesel-free borough by 2030.
Introduce emissions-based parking tariffs.
Phase out new residential parking permits for diesel cars.
Implement Zero Emission Zones in certain areas.
Create zero-emission loading bays and taxi ranks.
Pedestrianise high street areas, as is common across Europe.

We know that it will take longer to transition away from diesel vans, which is why the 2030 deadline needs to be set now. The UK Government needs to support industry to bring cleaner alternatives to market – current offerings are limited and expensive.