How millions of car owners could be owed compensation after landmark legal battle

Millions of motorists could soon be due compensation as a major legal battle have started in the High Court. Dozens of popular car manufacturers are alleged to have broken the rules over emissions as vehicle owners bring claims against them.

Five major car manufacturers are in court accused of cheating on emissions tests, with many more potentially facing a similar challenge based on the result of the challenge.

Mercedes, Ford, Peugeot/Citroën, Renault, and Nissan are the five companies involved, with all denying the accusations.

The trial marks a significant development in the ongoing “dieselgate” scandal, potentially impacting 1.6 million vehicle owners in what lawyers describe as the largest class action in English and Welsh legal history.

The companies face allegations that they used software which allowed their cars to reduce emissions of harmful gases under test conditions.

The five companies were chosen by the court as the lead defendants to be tried first. Nine other carmakers could face similar claims depending on the outcome of the case.

These are: Opel and Vauxhall, Volkswagen and Porsche, Jaguar Land Rover, BMW, FCA and Suzuki, Volvo, Hyundai/Kia, Toyota, and Mazda.

Here’s everything you need to know:

When did the issue begin?

The action follows the "dieselgate" scandal, which first emerged in September 2015 when Volkswagen was implicated by the US Environmental Protection Agency for installing defeat devices – software designed to manipulate nitrogen oxide emissions readings in its diesel vehicles.

The High Court confirmed in 2020 that Volkswagen had used these devices, breaching EU emission testing requirements. The carmaker later settled a UK class action for £193m with 91,000 drivers.

It has so far paid £27.8 billion globally, mostly in the US.

Beginning Monday, the High Court will determine if systems in diesel cars from five other manufacturers were similarly designed to bypass clean air laws.

These companies face allegations that defeat devices allowed cars to identify test scenarios, causing them to run at lower power and record artificially low nitrogen oxide emissions.

Lawyers for affected motorists argue their clients were deceived about the vehicles' environmental impact, and that these cars continue to emit dangerous levels of pollution on roads. A judgment is not expected until Summer 2026.

Will there be compensation?

If the court finds against the carmakers, a further trial to determine compensation payments to those affected would likely be in Autumn 2026.

If the court finds that sample vehicles assessed in the trial contained the defeat devices, then claimants will argue that this gives rise to claims for breach of statutory duty and contractual obligations.

Relying on case law from the Court of Justice of the EU (CJEU), they will also contend that consumers have a right to compensation for vehicles containing defeat devices.

While the exact amount that could be owed in each case would be subject to a long legal process, Leigh Day estimates it could be “thousands.” The law firm was the joint-lead lawyers in the original diesel emissions group litigation, and is one of the 22 law firms representing drivers at the High Court.

Leigh Day says it is now only accepting claims for vehicles manufactured by Volvo, which can not be heard as part of the ongoing case but can in further legal proceedings.

The deadline to make a claim with most other law firms has also now passed, but those who think they could be affected are advised to keep an eye on the proceedings for any updates that may impact them.

Speaking ahead of the trial, Leigh Day’s senior partner Martyn Day said: “A decade after the Dieselgate scandal first came to light, 1.6 million UK motorists now get their chance to establish at trial whether their vehicles contained technology designed to cheat emissions tests.

“Fourteen of the biggest car manufacturers operating in the UK are facing these claims which, if proven, would demonstrate one of the most egregious breaches of corporate trust in modern times.

“It would also mean that people across the UK have been breathing in far more harmful emissions from these vehicles than they were told about, potentially putting the health of millions at risk.”