A million motorists could each win thousands of pounds in compensation from Vauxhall after it was accused of cheating emissions tests.
The car maker is alleged to have sold about 600,000 diesel cars fitted with so-called defeat devices, designed to fool regulators.
Popular family models bought between 2009 and 2019 could be affected, including the Astra, Corsa and Zafira.
In all, a million customers who bought new, second-hand or leased cars could be entitled to payouts worth an average £2,500, according to lawyers Milberg London.
The law firm is preparing a mass claim, with an advertising campaign and website set to go live today.
It could be one of the biggest damages claims ever brought against a British car manufacturer and follows similar ‘dieselgate’ allegations against Volkswagen and Mercedes, which prompted vehicle recalls and court battles over compensation. Vauxhall last night denied the allegations.
A spokesman said the company ‘rejects any accusation of using illegal defeat devices’ and insisted ‘our vehicles meet the applicable regulations’. Edward Cardington, at Milberg London, said: ‘The Vauxhall Pay Up campaign has set out to prove Vauxhall cheated both the emissions tests and drivers.
‘Motorists were promised a combination of low environmental impact and high driving performance that appears to have been impossible in real driving conditions.
‘Put simply, clean diesel looks like a myth and we believe Vauxhall’s cars did not provide the performance drivers paid for.’
The law firm is planning a ‘group litigation order’ in which a large number of cases are treated as one by the courts. It says its claim is supported by ‘evidence from regulators, academic studies in the UK and Europe, and forensic analysis carried out by a global expert’.
Dieselgate erupted in 2015 when Volkswagen admitted to installing ‘defeat devices’ that made its diesel cars seem less polluting in tests than they really were on the roads.
The German manufacturer was forced to pay out more than £26billion in fines, compensation and buyback schemes.
If Vauxhall is found to be at fault, Milberg London says those who bought an affected car could be entitled to anything between 25 per cent and 75 per cent of what they paid.
For the average claimant they believe this would come to around £2,500.
That means if just one in ten eligible motorists comes forward, the case could be worth £250million, a spokesman said.