Largest-ever class action aims to expose diesel emissions
Wed, 12 Mar 2025
The UK’s largest-ever class action, which involves 1.5 million vehicle owners and aims to expose how many diesel cars used illegal ‘defeat devices’, is underway in the High Court.
The aim to decide what documents, said to be in the public interest, can be released, ahead of a full court case in the autumn.
Campaign group Mums for Lungs is among more than 50 organisations that want all documents to be disclosed, to expose just how many diesel cars were using illegal ‘defeat devices’ to cheat emissions tests.
The Department for Transport was ruled by the ICO in 2024 to have illegally withheld how many defeat devices operate.
The group points to research showing there are still 7.5 million Euro 5 and Euro 6 diesel cars on UK roads. "Cars certified to these standards were shown to be using defeat devices which cheat emission tests," the group says.
Separate research from the International Council on Clean Transportation suggested that 77% of Euro 6 and 85% of Euro 5 diesels have "suspicious" test results which could indicate the use of a defeat device.
Overall, there are nearly 10 million Euro 3-6 diesel cars still on UK roads, which are responsible for nearly 40% of the harmful NOx emissions produced by UK road transport.
Mums for Lungs recently protested outside the High Court and delivered an open letter to the judge calling for the disclosure of documents. This has been signed by two MPs, an NHS hospital and more than 50 charities and campaign groups.
"This looks like a sequel to the original dieselgate," says Mums for Lungs founder Jemima Hartshorn.
Cars with defeat devices are still on our roads she says, "polluting our towns and cities and making our children sick."
"We deserve to understand what is going on now – we need these documents to be made publically available due to the significant public interest in the matter."
As a result of the High Court action, the group says diesel cars from 13 leading brands could be recalled as a result of government action and the class action.
The first will involve Mercedes-Benz, Ford, Nissan/Renault and Peugeot/Citroen in October 2025.
Lawyers are also pursuing claims against Volkswagen, Porsche, BMW, Vauxhall, Fiat-Chrysler, Suzuki, JLR, Toyota, Hyundai-Kia and Mazda.
Mums for Lings also wants to see a £1bn fund from car manufacturers to pay for measures to phase out all diesel cars.
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