While diesel cars will initially carry a 3% company car tax penalty, Brown said: 'Developments in diesel after-treatment technologies have the potential to offer significant emission reductions, to the extent that some diesels could eventually have comparable emissions to the cleanest petrol carsFollowing proper evaluation of these emerging technologies, provisions will be put in place so the diesel supplement is waived for these very low-emission diesel cars.
'Consideration will also be given to the case for granting a discount, expressed as a percentage of the car's price, to these cars. Comments would be welcome on the nature of any exemption from the diesel supplement.'
The Government has traditionally been anti-diesel and defending the initial penalty - despite lobbying particularly by Peugeot - Brown said: 'Diesel cars emit less CO2 than petrol and so would be taxed on a lower percentage of the car's price if the charge was based purely on CO2 emissions. However, diesel cars emit greater quantities of the two local air pollutants of most concern - particulates and oxides of nitrogen.' Following consultation, Brown is also prepared to offer discounts to cars fuelled by alternative technologies.