DIESEL will still be a key fuel for fleet vehicles for the next 50 years, despite rapid advances in alternative technologies, a new report suggests.

Although fuel cells could be available by 2010, research by the Society of Motor Manufacturers and Traders' Future Fuels Strategy Group (FFSG) says diesel could be used to power light-duty diesel hybrids until the mid-21st century.

It says: 'For heavy-duty commercial vehicles (and perhaps for light-duty diesel hybrids) the continued use of diesel is foreseen well in to the mid 21st century.'

The report also warns that the advantage of using liquefied petroleum gas could diminish. 'As emission limits become more stringent, the benefits of LPG, other than a small carbon-dioxide emission reduction, will diminish.' The report identifies a 'consensus' among vehicle manufacturers and their partners that hydrogen promises to be a key fuel for the future, especially when made from renewable energy sources.

'The technologies appropriate for using hydrogen as road fuel are likely to be the electrolytic fuel cell or the familiar spark ignition engine,' says the report.

But it warns: 'On-board fuel cell storage is still an issue to resolve due to the low specific energy of hydrogen when compared to conventional liquid fuels.' According to the report, gasoline may have a role to play as an intermediate source of hydrogen.

'Towards a Shared Vision - Future Fuels and Sustainable Mobility' is the first report from the group, which has been set up to evaluate the long-term fuel options.

Christopher Macgowan, the SMMT's chief executive, said: 'The group's aim is to develop a vision for the future and to bring the alternative fuels debate to as wide an audience as possible.'