The car manufacturer Volkswagen subverted key air pollution tests, a British court has found, by using special software to reduce emissions of nitrogen oxides under test conditions.

The high court finding is a boost to attempts by campaigners to force the company to address the impact of its cars in producing lung-damaging pollutants at far higher levels than were legally permissible.

A group of about 91,000 claimants is taking Volkswagen to court in one of the biggest “class action” cases, or group litigation orders, yet to be heard in England and Wales. Although Volkswagen has been found guilty in the US, in Europe the carmaker has denied that it cheated tests.

The preliminary finding in the case on Monday, by Mr Justice Waksman, casts a fresh light on the activities of the carmaker, first revealed in the “dieselgate” scandal of 2015.

In his summary, the judge wrote: “[After considering the arguments made by Volkswagen] the upshot was that I found that the software function in the vehicles here did indeed amount to a prohibited ‘defeat device’… I also concluded that VW’s attempt to relitigate the issue here was an abuse of the process.”

He said: “A software function which enables a vehicle to pass the test because (artificially) it operates the vehicle in a way which is bound to pass the test and in which it does not operate on the road is a fundamental subversion of the test … it destroys the utility of the test.”

Volkswagen in 'Dieselgate' settlement talks with 400,000 German owners Read more

Diesel vehicles were once touted by the car industry as a green alternative to petrol vehicles because they have lower greenhouse gas emissions. But their emissions of tiny particles and irritant gases such as nitrogen dioxide are far higher, unless trapped by filters.

In 2015, campaigners revealed that cars produced by Volkswagen emitted far more nitrogen oxides in standard road driving than was recorded in test conditions. The ensuing scandal engulfed the car industry, which has faced turmoil and falling sales in some categories.

The revelations also highlighted rampant air pollution around the world, which is estimated to cause as many as 800,000 premature deaths every year in Europe alone.

In the UK, the sale of new diesel and petrol cars is to be banned from 2035, in an effort to clear up dangerous air and reduce the impact of road transport on the climate crisis.

Jenny Bates, a campaigner at Friends of the Earth, said: “Diesel exhaust is in the same category for causing cancer as smoking, according to the World Health Organization, so to deliberately hide this toxicity cannot go unnoticed or indeed unpunished. The sale of all diesel and petrol cars and vans should be banned by 2030, earlier than the government is planning, both for air pollution and climate reasons.”

Volkswagen is now likely to continue to a full trial of liability for the claims of deceit. The claimants argue that they were sold vehicles that were represented as being compliant with emissions regulations, when they did not comply.

A spokesperson for Volkswagen Group told the Guardian: “The judgment relates only to preliminary issues [and] does not determine liability or any issues of causation or loss for any of the causes of action claimed. These remain to be determined by the court as the case continues.

“Volkswagen remains confident in our case that we are not liable to the claimants as alleged and the claimants did not suffer any loss. We will continue to defend our position robustly. Nothing in this decision today changes this.”

33m polluting cars still on EU roads after Dieselgate scandal Read more

The group litigation order in the UK is brought against Volkswagen, Audi, Skoda, Seat, the Volkswagen financial services arm, and various authorised dealers, by owners and lessees of cars under these brands which used a particular Volkswagen diesel engine.

In the US, Volkswagen has paid out $4.3bn (£3.5bn) in civil and criminal penalties since pleading guilty more than two years ago to criminal charges based on deceit. Global costs are thought to have reached at least $21bn.

Gareth Pope, who leads the legal team at the Slater and Gordon law firm, representing 70,000 claimants, said: “This damning judgment confirms what our clients have known for a long time but Volkswagen has refused to accept: that Volkswagen fitted defeat devices into millions of vehicles in the UK in order to cheat emissions tests.

“The court’s conclusion that the existence of software was a ‘fundamental subversion’ of tests designed to limit pollution and make our air safe to breath exposes VW’s disregard for EU emissions regulations and public health, in pursuit of profit and market dominance.”