Car makers across the EU are "failing miserably" to meet their pledge to tackle climate change by reducing carbon dioxide emissions from their new models.
A study of Europe's car producers found that the industry managed to cut the CO2 output of new cars by 1 per cent last year - less than a quarter of the rate required to meet its own promise to cut emissions by 25 per cent in a decade.
Under a deal struck with the European Commission in 1998 to stave off compulsory regulation, manufacturers promised to produce cars which meet an average emissions target of 140g of CO2 for every kilometre by the end of 2008. But last year, the average figure was cut to only 160g/km. Some manufacturers, such as Mercedes and Land Rover, are producing vehicles with emissions well above 350g/km.
Campaigners said the time had now come to force car makers to reduce their impact on the environment by introducing binding targets for emissions.
Aat Peterse, of the Brussels-based pressure group Transport & Environment, which produced the report, said: "Europe's car makers are making vehicles which are bigger, heavier and more powerful than ever. The technology is already there to make cars produce significantly less CO2 but instead they trade any gain in engine efficiency with more weight and gadgets.
"Voluntary targets are clearly not working and the industry is failing miserably to meet them. Without compulsory targets, these promises will not be met."
Britain remains one of the worst offenders and, despite cutting CO2 levels by 11 per cent in the past seven years, it is almost certain to miss the 2008 target.
Sweden - where consumers prefer large-engined brands such as Volvo and Saab - has the highest CO2 output in the EU, almost 25 per cent higher than the country with the lowest output, Italy. The average new car sold in Sweden produces 195.8g/km, compared to 148.3g/km in Italy. In Britain the figure is 167.4g/km, the sixth-highest figure in the EU.
Campaigners said the figures showed that manufacturers were offsetting improvements in fuel efficiency by producing heavier cars to satisfy consumer demand for powerful vehicles. Transport is one of the largest contributors to global warming, accounting for 25 per cent of all CO2 produced in the world. Cars and vans account for 15 per cent of all CO2 in the EU.
But, while it has long been accepted that measures such as reducing engine size and improving fuel efficiency will cut CO2 emissions, car makers have been adding an average of 16kg to new cars each year in the form of air conditioning units and safety bars.
The current Volkswagen Golf has doubled in size and engine capacity since the first version was unveiled in 1975. The new Porsche Cayenne has more horsepower than the Second World War Sherman tank.
Transport & Environment estimates it would add just £400 to the cost of a new car to cut CO2 to 120g/km - the EU target for 2010. The emissions regime was agreed by the European Automobile Manufacturers Association (Acea), which represents the EU's 13 largest car makers.
The study found car makers will now need an average annual reduction in CO2 output of 4.3 per cent a year for the next three years to meet the 2008 target. Their best performance to date has been a cut of 2.9 per cent, in 2000.
In Britain, figures have fallen from 189.8g/km in 1997 to 174.2g/km in 2004. According to the same figures, only 481 of the 2.6 m illion cars sold in Britain emitted less than 100g/km.
Japanese and Korean manufacturers have also pledged to meet the EU emissions targets, calculated on the average output across each maker's fleet. But they have an extra 12 months to do so.
Representatives of the British car industry, which will unveil its own figures for carbon dioxide emissions on Tuesday, said that a combined solution involving consumers, the Government and oil companies was required. A spokesman for the Society of Motor Manufacturers and Traders said: "The 140g/km target was always going to be very challenging. We face competing requirements from the European Commission. Safety measures such as side impact bars and airbags add extra weight. You have to move that weight at the same speed which means you need more 'oomph'.."
But environmentalists claimthe manufacturers would make significant reductions in CO2 with simple measures, such as reducing the maximum speed of top-of-the-range cars from 155mph to 135mph.
Europe's CO2 monsters
* Ferrari SuperAmerica F1 (Italy)
Class: Supercar Cost: £198,800
Engine size: 5.48 litres
CO2 emissions: 499 grams per kilometre
* Porsche Cayenne Turbo (Germany)
Engine size: 4.5 litres
CO2 emissions: 378g/k
* Ford Galaxy 2.8i (Belgium)
Class: People carrier
Engine size: 2.8 litres
CO2 emissions: 295g/k
* BMW 7 Series 760Li (Germany)
Engine size: 5.9 litres
CO2 emissions: 325g/kReuse content