Saab has been rapped by the Advertising Standards Agency (ASA) for over-stating the environmental credentials of its BioPower range.
A Saab BioPower national press advert showed parallel horseshoe prints and tyre marks, and stated: 'More horsepower and a smaller carbon footprint.'
The advert stated that Saab's bioethanol engines, which run on fuel part-made from crops, reduced carbon dioxide emissions by up to 70%.
But the ASA ruled: 'We considered that readers were likely to infer that bioethanol did not add a significant amount of CO2 to the atmosphere.
'We considered that a 30% net addition to atmospheric CO2 was significant, and therefore concluded that the claim was likely to mislead.'
The ASA said that the advert broke rules on environmental claims, truthfulness and substantiation.
A Saab spokesman said the company had received only three complaints about the advert, but conceded that it could expand on some of the detail in the small print accompanying the advert.