Mayors and city leaders are calling for a £1.5 billion Government fund to take polluting vehicles off the UK's streets and improve air quality.
Mayor of London Sadiq Khan and UK100 - a network of local government leaders who are pushing for a shift to 100% clean energy by 2050 - are proposing the fund for a two-year national scheme on upgrading vehicles.
The call comes as mayors and city leaders from around the country are joined at a summit in London by Environment Secretary Michael Gove and Health Secretary Matt Hancock to discuss their concerns about air pollution.
Funding could pay for £2,000 credit towards an ultra low emission vehicle for scrapping a diesel registered by 2015 or incentives for cheaper public transport, car clubs and bikes for adults and families ditching such diesels.
It could also pay for £3,500 credit towards an ultra low emission vehicle for anyone scrapping commercial diesel vans and minibuses registered before 2016 and helping cities roll out low emission bus zones by upgrading existing vehicles and making the shift towards electric buses.
Half the fund should be ring-fenced for private citizens, with those on low incomes prioritised, and should be paid for with the £1.7 billion year-on-year savings the Government expects to see from its clean air strategy, its backers said.
The summit will also hear from NHS England chief executive Simon Stevens who is urging vehicle manufacturers to seize the opportunity provided by plans to upgrade the ambulance fleet to make them more environmentally friendly.
While the NHS long term plan has committed to ensuring nine out of 10 vehicles are low emissions within a decade, ambulances could not be included in the ambitions because green technology is not yet advanced enough to power the heavy vehicles with all the kit they carry.