Best in Class

City cars
Little cars like these have smaller engines, so they're an obvious low-emission choice.

Superminis
Small, efficient diesel motors have been widely developed for this segment and plenty of offerings now emit well under the 120g/km CO2 benchmark. In fact, the car with the lowest emissions in Britain is a supermini.

Small family cars
There's one hybrid - the Civic IMA - but don't expect many more in a smaller car segment like this. Instead, low-polluting diesel engines will be the way forward.

Large family cars
Which include the famous Prius hybrid. But that's not the end of the story here, as modern, mid-sized diesel engines pump out fewer carbon dioxide emissions than ever before.

Compact executive cars
Often all about performance, but rising company car tax has led to demand for greener models. As well as efficient diesel engines, biofuels are big in this segment and are being pioneered by Saab.

Executive cars
A new Lexus hybrid has shaken things up here, offering both relatively low emissions and high-performance. Still, our table shows that a number of diesel models are still greener in terms of CO2, although not as powerful.

Luxury cars
Typically a high-emissions zone. But a British car tops the green pile and performance diesels make up the best of the rest. That is apart from Lexus, of course, which compensates for its powerful petrol models with an all-new hybrid option.

Small sports cars
Perhaps surprisingly, not all sporty cars are that bad for the environment. Some of the best performers in this category produce supermini-levels of carbon dioxide emissions.

Luxury sports cars
Expensive and generally a bit flash, but not always massively polluting as our two list-topping diesels prove. Expect more hybrid options in this category over the coming years.

Four wheel drive
The big cars we love to hate. Fact is that some people need 4x4s, so who are we to judge? Besides, the most recent offerings in this class produce fewer CO2 emissions than ever before.

People carriers
Some of the biggest cars on the market, but ever-efficient diesel engines are helping to bring emissions down. Plus, if you divide the CO2 produced by the number of passengers one can carry (often seven), people carriers can make environmental sense.