Government and local authorities have been urged not to “demonise diesel” but to develop a national framework instead to encourage the take up of modern, clean diesel trucks.

The call came at a conference on air quality held by vehicle manufacturers’ association the SMMT.

While alternative fuels and drivetrains are available, diesel was currently the only practical fuel for trucks and most vans, said SMMT CEO Mike Hawes. “There are 4.4 million CVs on the road and 99% are powered by diesel,” he said. “They will remain diesel powered for some years to come.”

Chairwoman of the SMMT CV committee Penny Randall said the latest Euro-6 trucks were very clean, producing 98% less NOx and 97% fewer particulates than trucks did 25 years ago. But she admitted: “It will take many years for this new technology to permeate the industry.

“There is no alternative to diesel as yet and no quick or easy answer to the issue of air quality,” she said. “But it is time to stop demonising diesel and to start encouraging uptake of cleaner vehicles through incentives, rather than penalties.”

London is among 179 cities within the EU to face fines from the EC for failing to meet international air quality standards, with excessive NOx levels a major issue.

Elliot Trehane, air quality manager at the Greater London Authority, said 63% of NOx emissions came from transport, and of that 27% were from CVs.

The authority has set out a roadmap to be compliant with EU standards by 2020 that includes the introduction of an ultra low emissions zone in the worst affected areas of central London and around Heathrow.

Other UK cities are also considering low emissions zones and there are fears of a plethora of differing standards across the UK that will create difficulties for national operators.

Jon Lamonte, CEO of Transport for Greater Manchester, said the city was considering an LEZ but called for government to give the lead by setting a national agenda for air quality to set a level playing field.

“Leeds rejected an LEZ because of its economic impact,” he said. “By 2020 most vehicles will be Euro-6 but what do we do now? Don’t trouble us with EU fines – this is a national problem, not a local one.”

Mercedes-Benz head of engineering Nick Blake repeated the plea for joined up thinking and called for city authorities to use common EU standards that all vehicle manufacturers could work towards, rather than requiring CVs to be modified to meet local air quality standards.

In response Lamonte argued that “it is not a case that one size fits all – there are different challenges and priorities. We do respect standards, but a national framework is essential.”