THE most popular alternative fuel used by fleets could be made obsolete by developments in petrol and diesel technology, wiping out its status as a clean fuel, suppliers have been warned.

Transport Minister David Jamieson has called on producers of liquefied petroleum gas and vehicle suppliers to speed up development or risk losing vital tax advantages that have made the fuel popular.

He told LPG suppliers at the Liquefied Petroleum Gas Association's annual general meeting: 'The reason the Government introduced incentives for switching to LPG is that it delivered environmental benefits over conventional petrol and diesel vehicles. The game is moving on, though, and conventional vehicles are catching up and indeed overtaking LPG in the race to be clean.'

He warned that grants towards the extra cost of clean-fuelled vehicles through TransportAction PowerShift, and the future of fuel duty incentives which make LPG half the price of petrol and diesel were dependent on new developments in LPG technology.

'My colleagues at the Treasury will no doubt want to see the same evidence to justify any continuation of the significant fuel duty incentive that LPG currently enjoys. LPG appears to be struggling to keep up with the cleanest new petrol vehicles,' he warned.

In February, Jamieson gave his support to LPG as the fuel of the future at the launch of the 1,000th filling station, saying fleets that did not consider LPG-powers vehicles were were 'living in the past'.

He insisted this was still the Government's position, despite the tougher stance.

Jamieson added: 'We stand at a watershed. The danger facing us is that LPG stands still or moves backwards in the face of improvements in conventionally-fuelled vehicles. I do not want that to happen. I want to see UK companies at the forefront in developing this technology.'

The warning comes as two-thirds of fleet managers questioned in a recent survey by Calor said LPG was the most viable alternative fuel.