Their results are quite interesting. The top marques are, surprise, Toyota, not only because of the Prius, but thanks to clean diesel technology. Volkswagen follows, thanks to the availability of Bluemotion models across the range and a hybrid announcement. Third is Citroën, which has a lot of cars with low CO2 emissions, although the same can't be said for the upper models. Fourth is BMW which has brought "ecology" to the luxury car segment.
On the negative side there's Saab, which struck out due to the Swedish marque's bet on biofuels and the lack of biofuel support in the UK, as well as the lack of availability of smaller models. Then there's Mercedes, which was hit because they don't (currently) have any green technology vehicles on sale; the company's larger cars are available, though. Closing our the four worst list is the Land Rover, with a high CO2 average, and Mazda, which suffers due to a lack of an eco label. I bet they wish Econectic, parent Ford's green brand, could be handed down.