Governments should do more to help truck manufacturers introduce environmentally friendly technologies, according to a leading industry figure.
Ian Jones, UK managing director of Mercedes-Benz Commercial Vehicles, spoke as Royal Mail, Amey, DHL, Hill Hire, Ringway, Scottish and Southern, Tesco and TNT announced they would be trialling the company's Mitsubishi Fuso Canter Eco Hybrid vehicles in London over the next three years.
Jones says the firm was forced to invest £1.5m to convert the diesel-electric 7.5-tonne Canters to European Euro-4 standards, after requests to legislators for permission to operate the trucks using the Japanese Euro-4 equivalent proved unsuccessful.
About 300 Canter Eco Hybrids are already in service in Japan.
He adds: "Frankly, that money could have been better spent on supporting other environmental programmes.
"As we all know, it is difficult to establish any governmental support for those environmental projects. But I am not talking about specific sums allocated to individual projects, I am talking about creating an environment in which real partners can invest and see an appropriate return."
Jones says governments can also help the industry by removing congestion charges, stabilising fuel duty, encouraging alternative fuels, and freeing up bus lanes for environmentally friendly vehicles.
He believes diesel will remain the number one energy source for heavy commercial vehicles for the foreseeable future.
"In reality, the road to cleaner vehicles will not see a sudden transfer to a miracle fuel or a radically new engine technology," he adds. "It will be a process of stepping stones, of evolution and infrastructure development."