More green cars than gas guzzlers will be sold this year for the first time as drivers respond to rising fuel prices and environmental concerns.  Sales of new high-emission cars in the £300-a-year top road tax band fell last year by 15 per cent to the lowest level on record, according to industry figures obtained by The Times.

In the same period, sales of low-emission cars in bands A and B - which are either zero-rated for road tax or pay only £35 – leapt by 17 per cent.

The Society of Motor Manufacturers and Traders (SMMT) forecasts that sales of band G cars paying £300, such as the Porsche Cayenne and the BMW 7-series, will continue to fall sharply and will be overtaken this year by sales of band A and B cars.

Despite the publicity given to the Toyota Prius and other hybrid cars, which combine a petrol engine with an electric motor, most of the 128,646 low-emission cars sold last year had diesel engines. The least polluting conventional car, which delivers an average of 72 miles per gallon and emits only 99g of CO2 per km, 5g/km less than the Prius, is the diesel VW Polo Blue Motion, introduced last year.

The Government is planning to accelerate the shift to low-carbon cars by introducing extra green taxes on gas guzzlers and concessions for the greenest models. The changes, which may include a further widening of the price gap between each road tax band, are expected to be announced in the Budget in March.

Up to now, the Treasury has protected drivers of medium-sized cars from any significant increases in road tax. But a study commissioned by the Department for Transport and published last week found that people who drove cars in the middle tax bands were most likely to switch to greener cars if they had to pay higher taxes. People who drove band G cars tended to be wealthier and were more likely to absorb any extra cost.

Julia King, the Vice-Chancellor of Aston University, who was appointed by the Government to conduct a review of low-carbon cars, is planning to recommend a number of tax measures to encourage drivers to go green. These may include a purchase tax and extra incentives to encourage companies, which buy 55 per cent of new cars, to invest in greener fleets.

Professor King is particularly keen on the development of so-called plug-in hybrids, which have batteries that can be charged overnight on a green energy tariff, meaning that the first 40 miles driven each day would effectively be emission-free.

The European Commission has proposed a directive that would force manufacturers to reduce the emissions of the average new car from 160g/km in 2006 to 130g/km in 2012. The Government has hinted that it will allow the date for achieving 130g/km to move to 2015. This would help to protect British manufacturers of higher-emission cars, such as Jaguar and Land Rover.

Paul Everitt, the chief executive of the SMMT, told The Times: “We would be setting ourselves to fail if the target was 2012. We believe 2015 is more realistic because it gives us a practical timescale to develop the right mix of cars.” Mr Everitt admitted that manufacturers could do more to inform buyers about cars’ relative emissions levels. Most dealers now display colour-coded labels, similar to those used to indicate the efficiency of fridges and washing machines.

But manufacturers exploit loopholes in the regulations for car advertisements. They are required to give the CO2 performance of the models shown but can conceal the actual numbers by giving a range of figures in the small print, from the lowest-emission model to the highest. In many cases, the higher-emission models sell far more units than the lowest.

Mr Everitt said the SMMT was considering introducing new advertising guidelines that would make CO2 performance much clearers. However, he said that freedom of choice should be protected. “We are up for encouraging our customers to make sensible choices but manufacturers don’t want to be seen to be dictating to consumers.

“People buy cars for a variety of reasons and we can’t get away from the fact that a significant number of people see it as an emotional choice.”

Stephen Joseph, the director of the Campaign for Better Transport, said: “The SMMT figures show people are already changing their car-buying habits and that we should not believe the doom and gloom from car manufacturers about the impact of tough CO2 targets. The market will adapt.”

Source: Times Newspapers Ltd. By Ben Webster, Transport Correspondent