The advertising watchdog has told Vauxhall it must not infer the range-extended EV Ampera is capable of 360 miles on electricity alone.
It follows a TV advert which described the car as "driving electricity further" and mentioned about extended-range EVs "driven electrically at all times, even when an additional power source is generating electricity".
Further text stated "Ampera, up to 360 mile range."
The Advertising Standards Authority ruled the reference to an additional power source generating electricity was ambiguous, and that an average viewer would not understand that the car was in some circumstances being powered by electricity generated with a petrol engine.
"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," said the ASA.