A Lexus ad campaign claiming a four-wheel drive sports utility vehicle was environmentally friendly has been banned by the advertising watchdog.

The magazine ad campaign, for the Lexus RX 400h, was headlined: "High performance. Low emissions. Zero guilt."

Ten complainants to the Advertising Standards Authority believed the claims misleadingly implied that the car caused little or no harm to the environment.

They argued that the carbon dioxide emissions figure - 192g/km - was high compared with all other cars.

Lexus argued that within its particular category - SUV vehicles - the RX 400h had very low emissions, hence the claim.

The ASA agreed with this claim by Lexus. However, the watchdog added that the headline was misleading because it implied, incorrectly, that the vehicle's emissions were low in comparison with all vehicles and that therefore the SUV caused little or no harm to the environment.

It ruled that Lexus could not make such comparisons and claims of environmental friendliness in future car ads if they could not be proved.

The ruling came just two days after the Department of Transport launched its first TV campaign warning drivers about the dangers of climate change and the role that environmentally unfriendly vehicles are playing in increasing CO2 levels.

The DoT TV ad campaign, created by ad agency Leo Burnett, promotes the idea that drivers can reduce emissions by taking action such as making sure tyres are fully pumped up, keeping revs down and driving smoothly.

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