Fiat Chrysler and Renault face diesel emissions probes
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.
The US Environmental Protection Agency (EPA) said 104,000 Jeep Grand Cherokees and Dodge Ram trucks were affected.
The move comes as French investigators plan to probe Renault over suspected "cheating" in diesel emissions tests.
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.
The government has ordered tests on a Jeep Grand Cherokee, he said. "Our priority is to protect the interests of UK consumers."
The Jeep Grand Cherokee is sold in the UK, but the Dodge Ram is not.
According to the government, 3,700 Jeep Grand Cherokee cars have been registered in the UK.
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).
Meanwhile, French authorities said they would investigate Renault over suspected "cheating" in diesel emissions tests.
The Paris prosecutors office will conduct a probe into "cheating on key parts" of vehicles and into the quality of the tests.
The move comes in response to concerns raised last year by the French consumer protection agency, which carried out an investigation into several car makers in the wake of the Volkswagen scandal.
Three magistrates will now decide whether the company has a case to answer and should be put on trial.
A spokesman said Renault respected emission laws and did not use cheating software in its vehicles.
Shares in Renault were 1.6% lower in afternoon trading in Paris.
Analysis: Theo Leggett, business correspondent
When is a defeat device not a defeat device? When it's an auxiliary emissions control device, of course.
A defeat device is a piece of engine management software designed specifically to circumvent the emissions testing process. It can turn emissions controls on during the test, and off when the car is in normal use. Such systems are banned. Volkswagen has been fined billions for installing them on its cars in the United States.
However, the rules do allow very similar software programs to be used to protect the engine from damage, for example when it is warming up. They are capable of turning off emissions controls, but are referred to as "auxiliary emissions control devices". The problem is it can be very hard to tell the difference - which is why carmakers are supposed to keep regulators informed of what systems they are using.
This is a very grey area. Volkswagen engineers took a conscious decision to install devices on its cars because they could not get through tough US emissions tests any other way. But other companies have been accused of exploiting loopholes to boost the performance of their cars - at the expense of their environmental performance.
That is why Fiat Chrysler has been asked by the US authorities to demonstrate why its software does not constitute a defeat device - and why investigating judges in France will be asked to decide whether Renault has a case to answer.
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 BBC Radio 4's Today programme 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.
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.