Landmark Ruling Rejects Confidentiality Claims Ahead of Major Emissions Trial
In a significant legal decision, the High Court has ruled that five major car manufacturers involved in the Dieselgate scandal must disclose hundreds of previously confidential documents. These documents are expected to play a central role in a high-profile trial set to begin on 6 October 2025, examining allegations that certain diesel vehicles were equipped with illegal “defeat devices” designed to cheat emissions tests.
Who’s Involved?
The manufacturers at the centre of the ruling are Mercedes, Nissan, Renault, Peugeot/Citroën, and Ford. These five have been designated by the Court as “Lead Defendants” in the broader NOx Group Litigation, one of the largest group actions in UK legal history, involving around 1.8 million vehicle owners.
The trial will explore whether these manufacturers’ diesel vehicles were fitted with software designed to manipulate emissions during regulatory testing — a tactic known as the use of prohibited defeat devices.
Some of the manufacturers have made public statements defending themselves.
Mercedes Benz: “We continue to believe that the claims are without merit and will vigorously defend ourselves against them or any group action with the necessary legal means.”
Ford: “We see no merit in these claims and are robustly defending against them. Our vehicles and engines meet all applicable emissions requirements.”
Peugeot/Citroën, Nissan and Renault have made no comments.
Key Documents to Be Made Public
The documents to be disclosed include:
- Internal test results
- Engine design documents
- Communications with regulators
- Records of collaboration between manufacturers
These materials are considered crucial to the case, with lawyers for the claimants arguing that they contain evidence showing how emissions systems were potentially rigged to pass official tests while emitting far more pollution in real-world driving conditions.
Control your bills:
Energy Price Comparison* – Compare, Switch and Save over £250 per year
Car Insurance Price Comparison* – Save up to £523 per year
Broadband Price Comparison* – Broadband from as cheap as £19 per month
Boiler Insurance* with Home Emergency Assist – 35% off – Use code: REGULATORGUY
Justice Constable’s Damning Judgment
The judgment, delivered by Mr Justice Constable on 25 July 2025, followed a three-day hearing earlier in July. He ruled that the manufacturers’ widespread use of confidentiality designations was “overenthusiastic” and unjustified.
“The importance of the public being able to understand the substance of the claims against the Lead Defendants outweighs any commercial confidentiality in that material,” the judge stated.
He further emphasised that it should not be necessary for the public or press to physically attend the court to understand the case, and that legal pleadings and witness statements must be made publicly available in unredacted form.
Confidentiality Claims Rejected
The court dismissed the manufacturers’ arguments that the documents were commercially sensitive. Justice Constable found their claims to be:
- Generic and unsupported
- Not credible
- Lacking specific justification
He noted that the redacted pleadings made the case incomprehensible and highlighted the strong public interest in exposing potential corporate misconduct.
Even if some technical data had commercial value, the judge stated, the allegations involved prima facie credible claims of serious misconduct, making public access more important.
Trial Expected to Be Fully Open
The ruling makes clear that the October 2025 trial will proceed almost entirely in open court, with no significant reporting restrictions expected. Many of the documents previously designated as highly confidential will now be reclassified or made public.
Broader Legal Context
The trial of these five Lead Defendants is intended to pave the way for claims against other manufacturers implicated in the Dieselgate scandal. These include:
- Volkswagen/Porsche
- Jaguar/Land Rover
- BMW
- FCA/Suzuki
- Volvo
- Hyundai-Kia
- Toyota
- Mazda
- Vauxhall/Opel
A further trial, focused on potential compensation for vehicle owners, is scheduled for Spring 2026.
Legal and Environmental Advocates Applaud the Ruling
Martyn Day – Leigh Day
Martyn Day, senior partner at Leigh Day, welcomed the judgment:
“Given the huge number of claimants, it is crucial these documents can be accessed by the public and media to ensure full and thorough reporting of this corporate scandal. The principle of open justice is central to our legal system.”
He added that the overuse of confidentiality claims had delayed the case and resulted in hundreds of hours of unnecessary legal work.
Tom Goodhead – Pogust Goodhead
Tom Goodhead, Global Managing Partner of Pogust Goodhead, said:
“Excess emissions are not just regulatory violations – they are public health and environmental hazards. Today’s judgment sends a clear message: corporate attempts to suppress scrutiny will not succeed.”
He criticised the manufacturers’ efforts to push for a trial behind closed doors, calling them a waste of judicial resources and a threat to the principle of open justice.
Peter Gallagher – Pogust Goodhead
Peter Gallagher, Head of Product Liability and Supply Chain Litigation at Pogust Goodhead, highlighted the human cost of diesel emissions:
“In the UK alone, diesel emissions have been linked to 16,000 premature deaths and over 30,000 childhood asthma cases. Justice must not only be done — it must be seen to be done.”
Control your bills:
Energy Price Comparison* – Compare, Switch and Save over £250 per year
Car Insurance Price Comparison* – Save up to £523 per year
Broadband Price Comparison* – Broadband from as cheap as £19 per month
Boiler Insurance* with Home Emergency Assist – 35% off – Use code: REGULATORGUY
Environmental Groups Intervene
Representatives from ClientEarth and Mums for Lungs also made submissions at the July hearing. They argued that public access to the documents was essential for regulators to take appropriate action on vehicle emissions and ensure companies are held to account.
Manufacturers Sought to Limit Transparency
Lawyers for the manufacturers had proposed multiple measures to keep documents confidential during the trial. One suggestion included pausing the trial every time a sensitive document was mentioned to clear the courtroom of the press and public, as well as the legal teams for other manufacturers. Another proposal was to keep most documents sealed until after the trial concluded.
These measures were described by claimant lawyers as “ineffective and unworkable”, potentially amounting to a gagging of the press.
