Shown alongside extreme athletes, the advert launched in April highlighting the Ampera's 360-mile range with the slogan "Driving electricity further". A message at the start of the sequence said the comparisons were based on vehicles “driven electrically” but that an “additional power source” had been taken into account for the Ampera’s long range.

General Motors argued that the claims were true because the Ampera could be driven on its electric motors for 360 miles, adding that they were not intentionally misleading the public and that they were prepared to alter on-screen text.

But the ASA upheld the three complaints made, saying the additional power source was ambiguous and that most viewers unfamiliar with range-extending technology would not understand that the additional electricity was generated by a petrol engine.

‘We considered that throughout the ad the emphasis was on the fact that the car was being driven electrically, and that most viewers would not understand that the car was in some circumstances being powered by electricity generated with a petrol engine,’ the ASA said in its ruling.

‘The ad promoted an innovative product which many viewers would not immediately understand and we therefore considered that it would need to explicitly state that the car had a petrol engine. Because it did not clearly explain how the vehicle worked in extended-range mode, we concluded that the ad was misleading.’

Vauxhall has been told it cannot show the advert in its current form, and that future advertising should clearly explain how the drivetrain worked.