Mercedes is set to face a large fine for failing to meet the EU's targets on CO2 emissions, which are due to kick in from 2012. The German manufacturer is currently 31.4g/km away from hitting its target, and could end up paying as much as 750 Euros in fines for every car it sells in the UK.

Other manufacturers struggling to hit their targets are Mazda which is 23.1g/km over, Suzuki at 21.5g/km, and Chevrolet at 21.4g/km.

The EU set an overall emissions target for the car industry of 130g/km, but each manufacturer has an individual target based on the average weight of its range of vehicles. Smaller companies have to get below a lower level though, with Fiat having been set the lowest target of 111.1g/km.

Fiat is one of four manufacturers that have made it below the 130g/km average, along with Toyota, Mini and Citroen, and the Italian brand is currently leading the way with an average of 124.6g/km.

Toyota is likely to be the first company to hit its target, which was set at 124.7g/km. The manufacturer is just 0.34g/km away from meeting it, with its average emissions currently at 125.0g/km.

Mini and BMW are next in the list of manufacturers which are closest to their goals, being respectively just 6.4 and 7.0g/km away from meeting the required levels.

Jay Nagley, publisher of Clean Green Cars, which compiled the figures, said: "The fact that some manufacturers are very close to meeting the EU target shows up the failings of others. There are mainstream manufacturers which are still 30g/km of CO2 over their target, which is unacceptable."

Nagley reckons that it will take until the end of 2013 for many manufacturers to meet their targets, so there are likely to be many more companies other than Mercedes with fines to pay.