Diesel-powered vehicles will be banned from the roads of Athens, Madrid, Mexico City and Paris by 2025 as part of a pledge by the cities' mayors to improve air quality.

Decarbonising transport systems and promoting other options, including walking and cycling infrastructure, would help cut pollution and help deliver on the ambition of the Paris Agreement, the mayors said in a joint statement at a meeting of the C40 Cities Climate Leadership Group in Mexico.

They want manufacturers to stop producing diesel vehicles by 2025 and to support a rapid transition to electric, hydrogen and hybrid vehicles. ‘Mayors have already stood up to say that the climate change is one of the greatest challenges we face,’ said Anne Hidalgo, mayor of Paris and new chair of the group. ‘[Now] we also stand up to say we no longer tolerate air pollution and the health problems and deaths it causes – particularly for our most vulnerable citizens.’

The C40 also agreed to join with the World Health Organization and UN Environment Programme’s Climate and Clean Air Coalition (CCAC) to support a campaign to halve the 6.5 million deaths from air pollution by 2030.

The BreatheLife campaign will support city governments to reduce harmful emissions from the transport, waste and energy sectors, as well as mobilise citizen action to reduce air pollution while slowing climate change. ‘Ninety-two per cent of the world’s population live in places where air pollution levels exceed the WHO safe level for air pollution,’ said Helena Molin Valdés, head of the CCAC.

Meanwhile, London mayor Sadiq Khan has announced plans to more than double, to £875m, investment in improving the quality of the capital’s air until 2021–22. His predecessor, Boris Johnson, had pledged £425m.

Khan’s plans include introducing the world’s first ultra-low emission zone a year early, in 2019, and extending it to the North and South Circular roads for all vehicles, and potentially London-wide for lorries, coaches and buses.