The Volkswagen emissions scandal could now lead to Britain's biggest ever class action lawsuit.
The controversy is centred on "defeat devices" VW used to fool US emissions tests on diesel cars into believing the vehicles met environmental standards.
The company admits the software, which switches engines to a cleaner mode during official testing, may have been fitted in 11 million of its vehicles worldwide.
At least 482,000 cars are to be recalled and the car maker could face penalties of more than $18bn (£11bn) in the US alone.
VW Emissions Scandal: Key Questions Answered
A US law firm said on Wednesday it was suing Volkswagen in a class action lawsuit.
The global impact of the scandal is not yet known but drivers in the UK could find out later if their cars are affected.
Bozena Michalowska-Howells of law firm Leigh Day said: "The key issue in this country is whether or not these devices were able to bypass the European emissions tests.
"If it is shown that this piece of software defeated the European testing then Volkswagen would be in a very similar position as it is in the US and may well then have to call in their cars with all the resulting costs involved.
"This could well lead to one of the largest group claims ever in this country against Volkswagen for the way in which consumers may have been misled in relation to their vehicle."
The End Of Europe's Love Affair With Diesel?
Volkswagen's chief executive Martin Winterkorn quit on Wednesday saying he accepted responsibility for "irregularities found in diesel engines" but had not been aware of any wrongdoing.
He said in a statement: "I am shocked by the events of the past few days.
"Above all, I am stunned that misconduct on such a scale was possible in the Volkswagen Group."
VW has set aside an initial £4.7bn to cover the fallout and "win back the trust" of customers.
