Research by consumer magazine Which? has found that almost all diesel engines exceed emissions limits after being driven by motorists.
The study found that 95 per cent of diesel cars, as well as 10 per cent of petrol vehicles, emit nitrogen oxides above acceptable levels.
Out of 153 cars reviewed, the Jeep Grand Cherokee returned the worst results, emitting 15 times the amount of nitrogen permitted.
The news has come after Vauxhall was brought into the emissions limelight, after an investigation in Brussels found nitrogen emissions levels dropped dramatically following dealer services of the Zafira model.
Vauxhall admitted that 1.6-litre diesel powered-models were being investigated, but rejected the allegation that services were being used to rig emissions results.
A spokesperson for the carmaker told The Telegraph: "The software upgrade on the car is to do with a problem with a warning light that comes on too soon and tells you too soon that you need to put something in.
"It's nothing to do with emissions. It doesn't touch emissions or engine controls at all.
"The data provided by Emissions Analytics does not give us enough information to fully understand the results. We also need more info on the history of the test vehicle itself."
A Vauxhall spokesperson added: "We don't know how they are doing their testing."