Lawyers told the High Court on Monday that car manufacturers decided they would ‘rather cheat than comply with the law’ over vehicle emissions, as the largest class action in English history – dubbed the new ‘dieselgate’ – began.
Over 1.6 million motorists are taking legal action against more than a dozen manufacturers over claims that several diesel vehicles produced from 2009 onwards contained ‘prohibited defeat devices’ (PDDs).
Barristers representing the car owners claim that the devices allowed the vehicles to detect when they were being tested and alter the amount of harmful emissions produced so that they fell within emissions regulations.
This allowed the vehicles to pass emissions tests when actual outputs were much higher, which a trial in London has been told meant the cars breached regulations, and therefore meant there was a breach of contract.
The three-month case comes five years after a High Court ruled in 2020 that Volkswagen had installed unlawful defeat devices in thousands of its diesel vehicles, in a case that became known as the dieselgate scandal.
The vehicles in the current claims were made by Mercedes-Benz, Vauxhall, Nissan and Renault, Volkswagen and Porsche, Peugeot and Citroen, Jaguar Land Rover, Ford, BMW, FCA (the Fiat Chrysler Group now part of Stellantis) and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda.
The High Court was told that car manufacturers decided they would ‘rather cheat than comply with the law’ over vehicle emissions, as the largest class action in English history – dubbed the new ‘dieselgate’ – began on Monday
The cases against 20 ‘sample vehicles’ made by five manufacturers – Mercedes-Benz, Renault/Nissan, Ford, and Peugeot/Citroen – are now being heard as part of the initial phase of trial.
The main trial before Lady Justice Cockerill is due to conclude in December, but legal arguments will not be heard until March 2026.
The manufacturers are resisting the claims and deny that defeat devices were installed in their cars, with lawyers for Nissan describing the case as ‘fundamentally misconceived’ and barristers for Renault saying the claimants were ‘PDD hunting’.
Opening the trial, Thomas De La Mare KC, for the claimants, said: ‘What is really in play is an industry approach to calibration and technology selection over a considerable period of time.’
He said that ‘each player in the industry basically took a conscious decision that customer convenience, which helped the industry sell more cars, was more important’ than preventing pollution.
He added: ‘They have basically said the concern about making these cars sellable by removing these inconveniences is so strong, it is so valuable, it is such an important decision or fact in any consumer’s decision as to whether or not to buy the car, that we would rather cheat than comply with the law.
‘The law supports our case at every turn, and it is because the defendants have not followed the law.’
The main trial before Lady Justice Cockerill is due to conclude in December, but legal arguments will not be heard until March 2026. Protesters gather outside the Royal Courts of Justice in central London on Monday
VW is not one of the ‘lead defendants’ in the first part of the case beginning on Monday – although it is part of a larger group of defendants that could be affected by the eventual ruling with 115,232 Volkswagen Group vehicle owners part of the group action
In written submissions, the barrister also said the manufacturers had put forward ‘numerous improbable, even fanciful legal arguments’ over whether PDDs existed in the sample vehicles.
Those now taking legal action either bought, leased or otherwise acquired a diesel vehicle made by one of the companies, with most living in England and Wales.
The other manufacturers involved in the claims will be bound by the ruling that follows the trial.
The initial five manufacturer under the microscope are facing nearly 850,000 claimants out of the 1.6million total.
Mercedes-Benz has the highest volume of owners represented in the entire class action, which is the largest on record in England and Wales.
Some 374,774 Mercedes drivers account for more than one in five (22.9 per cent) of the 1,638,575 UK motorists being represented.
BMW (238,454), Vauxhall (193,951), Ford (175,244) and Renault/Nissan (148,893) make up the five manufacturers facing the largest number of claimants.
VW is not one of the ‘lead defendants’ in the first part of the case beginning on Monday – although it is part of a larger group of defendants that could be affected by the eventual ruling with 115,232 Volkswagen Group vehicle owners part of the group action.
While the ramifications of the trial could be costly for the wider motor industry, it will take some time for any compensation to reach claimants.
A judgment is not expected until summer 2026.
If the court finds against the car makers, a further trial to determine compensation payments to those affected would likely be in autumn 2026.
In July last year, barrister Benjamin Williams KC told a hearing that the proceedings could be worth at least £6billion.
The case centres around harmful nitrogen oxides (NOx) emissions, which are controlled by an emissions control system.
In his written submissions, Mr De La Mare said that a May 2025 report from the Centre for Research on Energy and Clean Air found that excess NOx emissions had caused 124,000 premature deaths and 98,000 new cases of asthma in children in the UK and Europe between 2009 and 2024.
The dieselgate scandal first emerged in September 2015. When VW admitted using these defeat devices, it led to the car maker having to pay more than €32bn (£27.8bn) in vehicle refits, fines and legal costs
How car makers responded
Alexander Antelme KC, for Renault, said in written submissions for trial that the legal action was based on the ‘false assumption that the features of the ‘VW Dieselgate’ applied across the entire automotive industry’.
He said: ‘The Renault core sample vehicles do not contain defeat devices or prohibited defeat devices, whether by accident or, as the claimants allege, deliberately to ‘cheat’ the emissions regulations.
‘The latter allegation is without merit and untenable.’
He continued: ‘The claimants’ case is riddled with errors and misunderstandings, especially about the design and operation of the vehicles’ emission control systems.
‘The features to which the claimants wrongly object are, in fact, appropriate and necessary elements of a well-designed diesel engine.’
Neil Moody KC, for Ford, said in written submissions that the case was ‘scientifically illiterate’ and ‘flawed on the facts and the law’.
He said: ‘Their case is not only that these vehicles were designed and marketed in breach of the emissions regulation; their case appears to be that these vehicles all contain PDDs as a result of deceit and fraud by all manufacturers.
‘The inference seems to be of some sort of industry-wide conspiracy. The proposition need only be stated for it to be seen to be implausible.’
The dieselgate scandal first emerged in September 2015.
The US Environmental Protection Agency accused Volkswagen of installing software – known as ‘defeat devices’ – on diesel cars to lower readings of nitrogen oxide emissions.
When VW admitted using these defeat devices, it led to the car maker having to pay more than €32billion (£27.8bn) in vehicle refits, fines and legal costs.
UK motorists seeking compensation in 2020 launched a High Court case against the German manufacturer to decide if it defeat devices had been installed.
VW settled those claims without any admission of liability in 2022.
The German auto giant agreed to pay £193million to the 91,000 motorists represented by law firms in the class action, which at the time was the biggest to be brought before the English courts. Volkswagen made a separate contribution to cover claimants’ legal costs and other fees.
Former chief executive Martin Winterkorn is also facing criminal charges for his role in the scandal. However, his trial was suspended on health grounds earlier this month.
Four other former Volkswagen managers have stood trial and were sentenced for their roles in the scandal in May.
Two receiving prison terms of several years for their role in the affair, while two received suspended sentences.
