CAR manufacturers decided they would “rather cheat than comply with the law” over vehicle emissions, the High Court heard today.

About 1.6 million motorists are taking what is the biggest legal action of its kind in English history against more than a dozen manufacturers.

The case is over claims that several diesel vehicles made from 2009 onwards contained “prohibited defeat devices” (PDDs).

Barristers for the motorists claim that the devices installed in the cars 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, there was a breach of contract.

The hearing follows a High Court ruling in 2020 that Volkswagen installed unlawful “defeat devices” in thousands of its diesel vehicles, in a case that became known as “Dieselgate.”

Vehicles in the current claims were made by Mercedes-Benz, Opel and Vauxhall, Nissan and Renault, Volkswagen and Porsche, Peugeot and Citroen, Jaguar Land Rover, Ford, BMW, FCA and Suzuki, Volvo, Hyundai-Kia, Toyota and Mazda.

The cases against 20 “sample vehicles” made by five manufacturers — Mercedes-Benz, Renault, Nissan, Ford, and Peugeot and Citroen — are now being heard at a three-month trial that began today.

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.

“They have basically said the concern about making these cars sellable by removing these inconveniences is so strong... 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 manufacturers are resisting the claims with barristers for Renault saying the claimants were “PDD hunting."

The main trial before Lady Justice Cockerill is due to conclude in December, but legal arguments will not be heard until March 2026.

A ruling is then expected next summer, with a further trial to determine any compensation scheduled for autumn next year.