Despite all the publicity and some high-profile champions of greener motoring, hybrid cars and other ecologically sound vehicles are just too pricey for most consumers, discovers Transport Editor Barrie Clement

Politicians recently decided to enhance their green credentials by trumpeting the ecological sensitivity of their cars. Unfortunately, it seems to remain, however, a preoccupation of the Westminster elite and a small minority of middle class motorists.

Environmentalists are fighting the price consciousness of the average driver and the continuing allure of the mechanical beasts with engines capable of propelling medium-sized planes. By far and away the "dirtiest" car on Britain's roads was, until recently, the astronomically priced Maserati MC12, according to the Energy Saving Trust, a non-profit-making body.

At a huge 545g/km, its massively flatulent exhaust system pumps out nearly four times more than the 140g/km target for carbon emissions for 2009 set by the European Union. On any given trip, the MC12 emits nearly seven times the amount of CO2 than the "hybrid" Honda Insight - the cleanest car generally available, which uses petrol on long runs and electricity around town.

The MC12 is a boy racer's dream with a six-litre engine, capable of reaching 62mph in 3.8seconds. However, the £560,000 price tag placed it beyond the wildest dreams of even those with more money than sense. The good news for the environment is that only three MC12s were sold in Britain in 2005.

Considerably more impact on the planet is being wrought by other upmarket gas guzzlers such as the Bentley Continental, the 14th dirtiest, and the Rolls-Royce Phantom, cruising at 17th in the trust's league table, which sold 1,923 and 1,484 respectively in 2005.

Of the off-road vehicles, by far the biggest single group of high-CO2 emission cars, the Porsche Cayenne is thought to produce the most carbon dioxide with 341.3g/km, closely followed by the Range Rover, 326.3g/km. A recent survey by the Society of Motor Manufacturers and Traders found that Warwickshire - home to Land Rover's headquarters at Gaydon and the nearby plant at Solihull - has the highest carbon emissions from new cars. One explanation was thought to be that Land Rover staff enjoyed substantial discounts on their four-wheel drives.

However, it's Britain's best selling cars that make the overwhelming contribution to the toxic clouds above Britain's motorways. The worst offender among the top 20 best-sellers is thought to be the Mondeo 1.8LX, which emits 182g/km of CO2 - the gas thought to be largely responsible for climate change. That is some way above the EU's 140g/km target. Only the Vauxhall Corsa 1.2 16v SXi fits the bill with 139g/km - although there are Toyota, Renault, Nissan and Volkswagen models which are there or thereabouts.

Interest in car emissions was given something of a boost recently when David Cameron, the Conservative leader, publicised the fact that he had chosen a 3.5-litre Lexus GS 450h as his official car. The Lexus combines a petrol engine with an electric motor that uses power otherwise wasted (eg, during braking) stored in batteries. The hybrid vehicle's 186g/km rating places it above the relatively "dirty" Mondeo, but substantially below the other luxury performance cars with petrol engines in its class which normally pump out between 200 and 300g/km.

It doesn't compare quite as well with competitor diesels from BMW, for example. Mr Cameron's environmentally friendly decision to opt for a bicycle in town was undermined by the fact that his papers are transported behind him in the Lexus, rather than in a pannier on his bike.

Despite the preoccupations of the Leader of the Opposition, it is clear that car buyers are generally more interested in price and specification of alternative models than their impact on rising sea levels.

Even newer models are not as clean as they might be. The average new car sold in 2005 emitted 10.7 per cent less CO2, but the rate of improvement is slow. The year-on-year average decline in emissions - from 171.4 g/km in 2004 to 169.4g/km last year - amounts to a drop of only 1.2 per cent. At this rate it will take Britain until 2022 to meet the target set for 2009. Cars in Britain also tend to have significantly higher emissions than the European Union average of 161.7g/km.

There is a degree of consumer resistance. A survey by Auto Express found that drivers believed eco-friendly cars were too expensive or offered too little choice. Readers were asked whether they would switch from a normal petrol or diesel car to a hybrid, such as the Toyota Prius or Honda Civic Hybrid, or one that runs on clean burning Liquid Petroleum Gas (LPG) or bioethanol.

Overall, 80 per cent of respondents said they would not switch. Of those who answered "No"; 64 per cent said there was no model that "fitted their buying criteria" and 55 per cent said green cars were too expensive. Around a third said that a lack of investment in any new fuel by ministers could ultimately render any green car they bought obsolete.

A similar proportion said any benefits of buying them - such as congestion-charge exemption or reduced car and fuel tax - could be withdrawn by politicians and that there would never be enough filling stations for clean fuels such as bioethanol and LPG. Last week's announcement that there will be no government grants for greener cars will not help matters either.

David Johns, Auto Express editor-in-chief, argued that the statistics would make worrying reading for those who were busy cultivating their green credentials. "It shows that car buyers simply don't trust politicians enough to make the leap of faith and invest in one of the new eco-friendly models."

While Auto Express has something of a following among "petrolheads", there is a general agreement that there is still a lot to be done to make motorists environmentally sensitive. Philip Sellwood, chief executive of the Energy Saving Trust, says that most people simply don't realise that road transport is responsible for a quarter of Britain's CO2 emissions and that they are rising at an "alarming" rate.

Motorists should also be more conscious of the way they drive, he says. "By driving smoothly, avoiding harsh acceleration and heavy braking, turning off the engine when stuck in traffic and changing gears at low revs, drivers can save 10 per cent on fuel." Perhaps a more impressive argument is that green cars can be cheaper to run.

Greg Archer, director of the Low Carbon Vehicle Partnership (LowCVP), pointed out that a family car like the Honda Civic Hybrid would cost the average motorist about £700 a year in fuel, whereas vehicles of a similar size can cost the driver more than £1,700.

Mr Archer says: "Most car buyers don't realise that by looking around it's possible to identify models with more than double the fuel economy of similar vehicles. Some of these are hybrids, others efficient diesels. If it's not convenient to switch to a smaller car you can still significantly reduce your fuel costs."

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