Leaders of cities across the UK are calling on the government to provide a £1.5bn fund to remove polluting vehicles from the streets.

Sadiq Khan, the mayor of London, is proposing the fund alongside UK 100, a network of local government leaders who hope to shift the nation to 100 per cent clean energy by 2050.

The money would be used for a two year national scheme designed to upgrade vehicles to lower emission alternatives.

The scheme's backers hope that this would improve the UK's air quality.

"Air pollution is a national health crisis," said Polly Billington, director of UK 100. "Government should work in partnership with local leaders by providing new powers and adequate funding: that will make a real difference to drive urgent and effective action.

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"Many councils and mayors are acting, but an extra £1.5 billion is needed to support people and businesses to switch from older polluting vehicles into low emission transport, cycling and walking so we can all love clean air. We also a need a new clean air law including tougher, legally binding World Health Organisation air pollution limits and an independent watchdog that will hold Government to account."

The scheme's backers said that the funding could pay for a £2,000 credit towards an ultra low emission vehicle, for scrapping a diesel registered by 2015 or for cheaper public transport and car clubs.

Another suggestion is that cities could spend the money on electric buses and low emission bus zones.

The group also said that half the fund should be ring-fenced for private citizens, with those on low incomes prioritised.

The fund has been proposed as mayors and city leaders meet Michael Gove, the environment secretary and Matt Hancock, the health secretary, at a summit in London focused on air pollution.

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"Tackling air pollution needs strong collective action," Mr Gove said. "I'm keen to work constructively with local government leaders in developing their plans and considering what further action is required ahead of the Spending Review."

The forthcoming Environment Bill would include new legislation on air quality, he added.

"We will deliver on our promise of a green Brexit with a strong new independent body to hold the government to account as we leave the EU," Mr Gove said.