The UK Department for Transport has asked for details of a US probe into Fiat Chrysler diesel emissions software as a matter of urgency.
The car maker has been accused of not telling authorities about software that could allow excess diesel emissions in thousands of vehicles.
US regulator the Environmental Protection Agency (EPA) said 104,000 Jeep Grand Cherokees and Dodge Ram 1,500 trucks were affected.
Fiat has rejected the allegations.
A Department for Transport spokesman said it was “urgently seeking further information” from the EPA as well as Fiat Chrysler about vehicles sold in the UK.
“Our priority is to protect the interests of UK consumers … the department’s new Market Surveillance Unit has the ability to test these vehicles if necessary,” he said.
The Jeep Grand Cherokee is sold in the UK, but the Dodge Ram is not.
According to industry body the Society of Motor Manufacturers Traders, 4,235 Jeep Grand Cherokees were sold in the UK between 2014 and 2016.
Fiat Chrysler chief executive Sergio Marchionne said on Thursday that the company had done nothing illegal.
“There was never any intent of creating conditions that were designed to defeat the testing process. This is absolute nonsense,” he added.
The EPA said Fiat Chrysler could be liable for fines of about $44,500 per vehicle, which could mean a total of about $4.6bn (£3.8bn).
On Wednesday, Volkswagen pleaded guilty to three criminal charges to settle US charges over its emissions-rigging scandal that affected almost 600,000 diesel vehicles. It will also pay fines of $4.3bn (£3.5bn).
John German, of the International Council on Clean Transportation, told the BBC’s Today programme that a distinction should be drawn between VW and Fiat Chrysler (FCA).
“VW had software embedded that looked for the actual test cycle used for regulatory purposes, and when they recognised it they turned the emissions controls on, and all other times they shut the emissions controls off. So in the real world, the emissions controls were basically off all of the time,” he said.
“FCA has not done this – they’re looking at things like vehicle speed, vehicle acceleration, and shutting the emission controls off some of the time in the real world, but not all of the time.”
Mr German said that although emissions from Fiat Chrysler engines appeared to be higher in the real world, it was not clear whether this was deliberate.
“It has to do with how exemptions from the defeat device regulations are interpreted in Europe and in the US, and so it could have been just more ignorance on the part of the Fiat Chrysler people who were calibrating this engine,” he said.
The UK is facing legal action by the European Union over the Volkswagen emissions scandal.
The chair of the Commons Environmental Audit Committee, Mary Creagh, told the Today programme that the government had been “too slow” to act against VW compared with the US.
Only 160,000 of the 1.2 million affected vehicles in the UK had been fixed, she said.
“Here we are in the UK… no immediate prospect of action from the government, although I understand from ministers that they are keeping that option open. It certainly seems that we are soft-pedalling.”
Question of timing
Jim Holder, editorial director for Haymarket motoring magazines, said that the EPA investigation into Fiat had been going on for 18 months, and that the company had been “waiting for the Trump administration to come into power”.
President-elect Donald Trump is planning to appoint a new EPA head who may be softer on these issues, Mr Holder said.
By taking action against Fiat now, the EPA had ensured the process had begun before Mr Trump took office, he added.
Meanwhile, a French investigation into possible emissions cheating by carmaker Renault has taken another step.
At the instigation of the Paris prosecutor, three judges have been looking at whether the matter should be brought to trial, according to the Reuters news agency.
Renault shares fell sharply on the news, which comes about two months after the government passed the findings of an investigation by its consumer fraud agency to the prosecutor.
The French investigation was launched in the aftermath of the Volkswagen scandal.