Several of the world's biggest car manufacturers have avoided a major legal blow after the High Court ruled that most of the diesel vehicles at the centre of the UK's largest-ever emissions lawsuit did not contain illegal emissions-cheating devices.

The case involved claims from around 1.6 million motorists who alleged that manufacturers including Mercedes-Benz, Ford, Nissan, Renault, Peugeot and Citroën had fitted diesel vehicles with unlawful "defeat devices" designed to manipulate emissions tests in a scandal compared to Volkswagen's infamous "Dieselgate" affair. However, Mrs Justice Sara Cockerill found that the vast majority of the technology used by the manufacturers did not meet the legal definition of an illegal defeat device.

While the ruling was largely in favour of the carmakers, the court did identify limited issues involving a discontinued coolant temperature control system in certain Mercedes-Benz models and a "split-injection" strategy used in some Peugeot and Citroën vehicles. Those findings could still be subject to further legal proceedings, with both manufacturers and claimant lawyers considering appeals.

The judgment represents a significant setback for claimants seeking compensation, although the wider litigation is not yet over. Further hearings are expected later this year to determine whether the limited findings against some manufacturers could lead to damages. The case is separate from Volkswagen's 2015 Dieselgate scandal, in which the German automaker admitted installing software specifically designed to cheat emissions tests, triggering billions of pounds in fines and compensation worldwide.