Hearing calls for transparency in Dieselgate

On 7 July 2025, the High Court of Justice will oversee a crucial hearing concerning the Dieselgate Litigation, one of the largest group actions in English legal history. The case involves approximately 1.6 million car owners pursuing claims against major automotive manufacturers, including Mercedes-Benz, Ford, Nissan, Renault, and Peugeot-Citroen, for allegedly fitting vehicles with illegal emissions “defeat devices”. These devices reportedly manipulate emissions control systems, allowing cars to emit nitrogen oxide (NOx) levels exceeding legal limits when driven normally. As the October 2025 trial approaches, questions about confidentiality will take centre stage.

Ahead of the trial, automotive manufacturers have filed redacted documents that anonymise details on how, and when, these alleged defeat devices operate. In an attempt to promote transparency and protect public interest, community interest group Mums for Lungs and environmental law organisation ClientEarth are petitioning the Court to unredact this information. They argue that key materials could reveal how emissions control devices function, including the conditions under which they fail to operate effectively, potentially keeping vital information away from scrutiny at a time when air quality remains a pressing public health concern.

Mums for Lungs has formally requested that the Court comprehensively review the redacted documents, given the high public interest surrounding the case. Their open letter to the Court, signed by over 650 individuals, underscores this urgent need for transparency. "The impact of air pollution on people’s health remains a live and urgent issue. Emissions from diesel cars are a major contributor to air pollution," stated Jemima Hartshorn, Founder and Director of Mums for Lungs. Children are particularly susceptible to the adverse effects of NOx emissions, which have been linked to severe health issues including asthma.

The outcome of the 7 July hearing will have significant implications for the upcoming trial, which aims to determine the legality of defeat devices fitted in vehicles. If these redactions persist, much of the trial could unfold behind closed doors, without public access to crucial technical details. This lack of transparency may prevent consumers and regulatory bodies from understanding the full extent of the harm caused by emissions from these vehicles.

ClientEarth’s campaigner, Andrea Lee, emphasised the importance of accountability, stating, “The scale of harm caused by unlawful and unsafe diesel emissions demands transparency from the auto manufacturers.” The investigations launched by the UK Government following ClientEarth's complaints demonstrate that the fallout from Dieselgate could extend beyond the courtroom. However, these efforts are currently hampered by delays and insufficient transparency.

Lawyer Shazia Yamin, representing Mums for Lungs and ClientEarth, reinforced the significance of open justice, highlighting that the case addresses essential questions about public health and environmental responsibility. “Our clients are seeking to bring into the open important information that affects us all,” she said. As the 7 July hearing approaches, the industries’ practices and the impact of diesel emissions will remain under the spotlight, with potential ramifications that could influence future litigation tied to the Dieselgate scandal.