The largest group action lawsuit in English legal history reconvened in the High Court today as solicitors representing 1.6million UK drivers accuse more than a dozen car makers of installing illegal ‘defeat devices’ in diesel models sold after 2009.
The court case comes more than a decade on from the original ‘Dieselgate’ scandal, which saw Volkswagen pay out tens of billions in vehicle refits, fines and legal costs.
The UK litigation brings proceedings against 14 different car brands.
Lawyers representing UK drivers in the ‘Dieselgate 2’ case previously valued the blowback at £6billion if these car firms are found guilty of using software to actively cheat emissions tests, resulting in diesel models producing far higher levels of toxic pollution under real-world conditions.
The hearings, which will last three weeks until Friday 20 March, will see lawyers representing vehicle owners and 14 major car manufacturers make their closing submissions to the judge, Lady Justice Cockerill.
A verdict is expected in the summer, with a secondary trial if car makers are found guilty to determine the level of compensation to be paid out.
Leigh Day and Pogust Goodhead are the two lead firms among 22 in total representing the 1.6 million vehicle owners bringing the legal claims in the largest group action ever seen in England and Wales.
Expert witnesses and evidence was submitted before the judge during twelve weeks of hearings that took place from October to December 2025.
Of the 14 vehicles makers involved in the lawsuit, five were selected by the court to be ‘lead defendants’.
These are representing the wider industry against claims of using unlawful technology to cheat official emissions tests due to the unprecedented scale of the legal claims and to save time and reduce costs.
They include Mercedes-Benz, Ford, Renault, Nissan and Stellantis-owned Peugeot and Citroen.
However, the remaining brands are also able to submit their own defences over the coming three weeks as part of the next phase in the legal case.
In terms of the volume of claimants, those facing the most accusations are Mercedes (373,774), BMW (238,454), Vauxhall (193,951), Ford (175,244) and Renault/Nissan (148,893).
Campaigners pictured outside the Royal Courts of Justice in central London on Monday 13 October as the largest group litigation case in English legal history kicked off at the HIgh Court
Speaking as the Dieselgate trial resumed in the High Court, Leigh Day’s senior partner Martyn Day said: ‘We are now entering the final part of this liability trial to determine whether the vehicles of 1.6 million motorists contained technology which enabled them to pass emissions tests despite producing far higher levels of pollution when driven on the road.
‘The High Court has already heard 12 weeks of evidence which our clients allege shows many of the biggest car manufacturers in the UK installed these so-called ‘cheat devices’ in their vehicles.
‘If proven, this would be a major breach of corporate trust and would mean millions of people across the UK have been breathing in far more harmful emissions from these vehicles than was permitted.’
He added: ‘The judgment in the case, which is anticipated by the summer, will be a landmark moment with potentially huge implications for millions of drivers and the automotive industry as a whole.’
Vehicle owners claim their cars were fitted with ‘prohibited defeat devices’ or PDDs for short – which can detect when the cars were being tested and ensure emissions were kept within legal limits.
When the vehicles were driven on the road, it is claimed they produced far higher levels of emissions, polluting the environment and creating a greater risk to public health.
As well as the five lead defendants, Vauxhall, Volkswagen-Porsche, Jaguar Land Rover, BMW, FCA-Suzuki, Volvo, Hyundai-Kia, Toyota, and Mazda all face claims that their vehicles contained similar emissions-cheating devices.
All the cases will be impacted by the judgment in the lead case trial, which is expected to be delivered in the summer.
A further trial to determine the level of compensation which may be due to the vehicle owners is scheduled to take place in the autumn.
The dieselgate scandal first emerged in September 2015. The US Environmental Protection Agency accused VW of installing defeat devices to lower readings of nitrogen oxide emissions
Resumption of the group action case on Monday 2 March comes just days after the Department for Transport confirmed it is conducting its own probe into the potential use of unlawful defeat devices.
In a Westminster Hall debate on Wednesday 25 February, Labour MP Rupa Huq called on the Government to accelerate its plans to enforce punishments against companies found to have used illegal emissions devices in the past, present and future.
The MP for Ealing Central and Acton referenced the case of nine-year-old Ella Adoo-Kissi-Debrah who in 2020 became the first person in the world to have ‘air pollution’ listed as a cause of death on her death certificate.
Ella, who lived 25 metres from the South Circular Road in Lewisham, died following an asthma attack in 2013, with an inquest later finding air pollution made a material contribution to her death.
Dr Rupa Huq MP said: ‘Clean air is not a luxury – it is essential. We would not force-feed a child dirty water, yet we expect them to breathe toxic air. Environmental standards must mean what they say.
‘If unlawful defeat devices have been used, there must be transparency, accountability and decisive enforcement.’
Responding for the Government, transport minister Simon Lightwood MP confirmed that the Driver and Vehicle Standards Agency (DVSA) since early last year has been conducting its own ‘targeted and comprehensive programme of assessments to assess a range of Euro 5 and Euro 6 diesel cars and vans produced between 2010 and 2018’.
Lightwood said there are 110 individual vehicle models under active investigation, confirming the DVSA had completed some initial assessments but is now ‘reviewing detailed submissions from manufacturers, with further assessments underway’.
While the investigation carried out by the DVSA is separate from the expert witness statements and evidence supplied as part of the group litigation, Daily Mail and This is Money understands the Government has been in communication with solicitors regarding their findings that have already been submitted to the judge.
Once the results of the DVSA’s investigation have been formalised, Lightwood said the Government would take swift action against any of those found to be in breach of the law.
‘Let me be clear: if non-compliance is confirmed, the DVSA will require manufacturers to take whatever remedial action is necessary, at no cost to consumers,’ he told the debate.
‘Where any serious risk is evidenced, that remedial action must be taken without delay.’
Since 2018, the use of defeat devices in vehicles has been a criminal offence.
The dieselgate scandal first emerged in September 2015.
The US Environmental Protection Agency accused Volkswagen of installing 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 global recalls, fines and settlements.
Following a High Court trial in the UK in 2020, Volkswagen 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 also made a separate contribution to cover claimants’ legal costs and other fees, however, the settlement was reached without any admission of liability in 2022.
Former Chief Executive Martin Winterkorn was also scheduled to face criminal charges, though his trial was suspended on health grounds last year.
Four other former Volkswagen managers were sentenced for their roles in the scandal in May with two receiving prison terms of several years for their role in the affair, while two received suspended sentences.