The Department for Transport, in association with What Car?, has developed a ranking system that helps buyers find the most environmentally friendly vehicles. To find out more about Act On CO2 click here.
We recommend some green superminis as well as listing the best in class based on their CO2 rankings.
Environmental issues come first, but we've also taken into account what the cars are like to drive, own and live with.
What Car? Recommends
1 Fiat 500 Start & Stop
Being green doesn't mean being boring, as the 500 proves. It's not only one of the cleanest superminis around, but also one of the most desirable. Adding a stop-start system to the standard car drops its emissions to 113g/km and raises its economy to 58.9mpg - and all without sacrifcing any of the car's appeal. This model is as chic and smart as any 500, and well equipped, too.
2 Ford Fiesta 1.6 TDCi Econetic
Ford’ latest Fiesta is our favourite supermini with a 1.25-litre petrol engine. It’s not surprising, then, that the Econetic model is one of our favourite small green cars. It’s not just the jaw-dropping 98 g/km CO2 output, either. Crucially, this version is also as stylish, good to drive and refined as any other Fiesta.
3 Toyota Aygo 1.0 VVT-i +
Not only is the Aygo a great budget buy, it's a great green buy, too, with some of the lowest CO2 and fuel consumption figures around. The small three-cylinder petrol engine knocks out just 109g/km in CO2 emissions, and although there are some inevitable sacrifices in a car this small and cheap, the low running costs make up for that.
The Aygo is mechanically the same as the Citroen C1 and Peugeot 107, so they have equally attractive green credentials. However, better resale values and Toyota's reputation for reliability make the Aygo a better buy than the two French cars.
1 Smart Fortwo Coupe 0.8 cdi 88g/km VED Band A 83.1mpg
2 Ford Fiesta 1.6 TDCi (90PS) 98g/km VED Band A 76.3mpg
= Seat Ibiza 1.4 TDI Ecomotive 98g/km VED Band A 76.3mpg
4 Toyota iQ 1.0 99g/km VED Band A 65.7mpg
= Volkswagen Polo 1.4 TDI BlueMotion 99g/km VED Band A 65.7mpg