Volkswagen installed unlawful “defeat devices” in thousands of its diesel vehicles, the High Court has found in the first major ruling on mass litigation brought in England and Wales over the “dieselgate” emissions scandal.

Around 90,000 motorists who bought VW, Audi, Seat and Skoda diesel vehicles have taken legal action for compensation in a case which could be the largest consumer action in English legal history.

Their lawyers say VW “cheated” European emissions standards, which were designed “to save lives”, by installing unlawful “defeat devices” in its diesel vehicles, meaning the vehicles were emitting up to 40 times the legal limit of nitrogen dioxide when out on the road.

In September 2015, Volkswagen Group announced that 11 million vehicles worldwide, including almost 1.2 million in the UK, were affected, prompting a flurry of litigation around the world.

The aftermath of the scandal has seen VW pay out more than 30 billion euros (£26 billion) in fines, recall costs and civil settlements, and has led to criminal charges by German prosecutors against current and former senior employees.

The English litigation was filed back in 2016, but reached what lawyers described as “a decisive court battle” at a preliminary hearing in December when the High Court was asked to decide whether software installed in VW cars was a “defeat device” under EU regulations.

In a judgment delivered remotely on Monday, Mr Justice Waksman ruled that “the software function in issue in this case is indeed a defeat device” under EU regulations.

The judge said he was “far from alone in this conclusion”, referring to “numerous courts and other bodies in various other jurisdictions (which) agree that the software function here is a defeat device”.

Mr Justice Waksman added: “While I take comfort from that fact, I make it clear that there is no need to resort to it because in my judgment the answer is so plain in any event.”

The judge also stated that “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 and the objective behind it”.

He added: “In other words, it destroys the utility of the test because it makes it impossible for performance under it to be the approximation of normal driving conditions and performance which it is intended to be.”

In a statement after the ruling, Gareth Pope, head of group litigation at Slater and Gordon, which represents around 70,000 claimants, said: “This damning judgment confirms what our clients have known for a long time, but which VW has refused to accept: namely that VW fitted defeat devices into millions of vehicles in the UK in order to cheat emissions tests.

“In the judge’s own words, VW’s defence was ‘highly flawed’, ‘hopeless’ and ‘absurd’.

“The case exposed VW’s approach to this litigation and its customers, refusing to admit wrongdoing and compensate its customers in favour of running drawn-out and pointless litigation.

“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 breathe exposes VW’s disregard for EU emissions regulations and public health in pursuit of profit and market dominance.

“VW’s utter failure to convince the court of the merits of its case means that now is surely time for it to settle these claims and put this shameful episode behind it.”