The Advertising Standards Authority has upheld a complaint about an advert by Aberdeen-based bus operator FirstGroup.

The advert, broadcast on television and the company's website, made misleading claims about the low carbon emissions of FirstGroup buses.

First aired on September 23, it claimed the companies buses "produce 4.97% less carbon than conventional diesel buses".

A viewer complained that the advert misled viewers about low carbon buses, which the Department for Transport says should produce 30% less carbon than normal diesel buses.

The ASA has upheld the complaint and ordered FirstGroup not to air the adverts again in their current form.

The watchdog ruled that the advert may confuse some viewers between teh FirstGroup buses and low carbon ones.

A First UK Bus spokesman said: "As a company we are committed to reducing the impact our fleet has on the environment.

"Our low emissions claim was in relation to our wider reaching corporate aims in respect of climate change rather than a comparison to Department for Transport’s benchmark, demonstrated by the use of qualifying on-screen text to avoid this being misleading."