Last year, new passenger cars emitted on average 119.6g/km, 8% below the official EU target set for 2015, although the average mass of new cars sold remained broadly the same.

The least fuel-efficient cars were bought in Estonia and Latvia (137 g CO2/km) followed by Bulgaria (130 g CO2/km). For all remaining member states, the average emission levels were below 130 g CO2/km. As seen in 2014, the Netherlands (101.2 g CO2/km) was the country that registered the most efficient new cars. Portugal and Denmark followed with new cars emitting on average 106 g CO2/km.

Diesel cars remain the most sold vehicles in the EU, constituting 52% of sales. As in past years, the countries with the highest proportions of diesel sales include Ireland and Luxembourg (71%), Portugal (69%), and Croatia, Greece and Spain (63%).

The research also found that the average fuel efficiency of petrol cars (122.6g/km) has been catching up with the fuel-efficiency of diesel cars (119.2g/km) in recent years.

Sales of plug-in hybrids and battery-electric vehicles continued to increase. The relative share of plug-in hybrids and battery-electric vehicle sales was highest in the Netherlands and Denmark, reaching 12% and 8 % respectively of national car sales in 2015. However, sales of such vehicles still remain a small fraction of total sales, accounting for just 1.3 % of all new EU cars sold.

Around 57,000 pure battery-electric vehicles were registered in 2015, a 50% increase compared to 2014. The largest number of registrations were recorded in France (more than 17,650 vehicles), Germany (more than 12,350 vehicles) and the UK (more than 9,900 vehicles).

However, in response, green transport group Transport & Environment said the figures are “worthless and the claimed savings hot air”.

The group claimed that: “The testing system is utterly discredited and the claimed fall in emissions is largely achieved through manufacturers manipulating the outdated tests. The reality on our roads is that the efficiency of new cars has been largely unchanged for four years.”

Greg Archer, clean vehicles director at Transport & Environment, added: “Official figures on carmakers’ new car CO2 emissions are hot air. Most of the measured improvement is being delivered through manipulating tests, not real-world reductions. The chasm between the reported data and reality makes today’s announcement worthless. Without a new test conducted by genuinely independent testing bodies, drivers will continue to be misled while the planet warms.”