The offer comes as part of changes to the Government-funded TransportAction PowerShift programme, which pays for up to 60 per cent of the conversion cost or extra purchase cost of alternatively-fuelled vehicles.
The announcement follows a consultation on the future shape of TransportAction PowerShift, launched earlier this year and includes a funding guarantee until 2004 to reassure fleets of long-term access to grants if they shift their purchasing policy to alternative fuels.
Before the changes, currently affecting England only, the scheme only paid for the purchase or conversion of vehicles up to one year old and the extension qualifies a further two million motorists to benefit from the scheme.
The scheme is mainly aimed at purchases of vehicles converted to run on petrol and liquefied petroleum gas, which is now available at about 800 refuelling sites throughout the country.
The level of grants depends on how much the conversion reduces the car's emissions and only officially approved kits, listed in the PowerShift Register, qualify for the grant.
Jonathan Murray, director of TransportAction, the umbrella organisation charged with encouraging drivers to shift to alternative fuels, said: 'This will give greater clarity and certainty to the marketplace, encouraging private drivers and fleets to use LPG.'
The extension of the grant scheme to cover vehicles up to five years old starts from next month. Transport Minister David Jamieson said: 'Our continued commitment to LPG and other clean fuels will give industry and transport operators the confidence to continue investing in cleaner vehicles and refuelling sites.'
- For further details, visit the PowerShift website.