Rishi Sunak has been urged by Sadiq Khan to fund a scrappage scheme for the home counties ahead of the planned expansion of London’s ultra low emission zone (Ulez).

The Mayor of London wrote to the Prime Minister asking him to provide financial support for people in locations such as Surrey and Kent who drive into the capital with the most polluting vehicles to scrap or retrofit them.

He also called on Mr Sunak to match the £110 million he has allocated for London’s scrappage scheme.

A Government spokesman said the mayor must “justify his decision” to extend the Ulez.

Mr Khan is planning to expand the Ulez to cover the whole of London from August 29 to boost air quality, with a £12.50 daily fee for vehicles not meeting minimum standards.

This has met fierce resistance from several councils, with five mounting a legal challenge partly based on the scrappage scheme.

In a letter, Mr Khan urged the Prime Minister to “become a doer, rather than a delayer, when it comes to climate action”.

He explained that several areas introducing clean air zones have received Government funding for scrapping non-compliant vehicles – such as Greater Manchester (£120 million), Bristol (£42 million), Birmingham (£38 million) and Bradford (£30 million) – but London and the home counties “have not received even a penny of support”.

The mayor wrote: “I urge you to use some of the unexpected £30 billion windfall in the public finances to not only match the funding allocated for scrappage in London, but to introduce a targeted scrappage scheme that provides help to those based in the home counties.”

He went on: “London, the South East and the East of England make net contributions to the Treasury every year, and Londoners pay £500 million of vehicle excise yearly, which is then spent on maintaining roads in other parts of the country.

“For our regions to pay in so much and not be helped to reduce carbon emissions and make our air safer to breathe is unfair and doesn’t make sense.”

I’m simply not prepared to stand idly by while toxic fumes from highly polluting vehicles choke our communities and leave our children reaching for inhalers and gasping for air

For diesel cars and vans to avoid the Ulez charge they must generally have been registered from September 2015, while most petrol models registered after 2005 are exempt.

London’s scrappage scheme for vehicles that do not comply with the emissions standards includes payments of up to £2,000 for eligible drivers such as those on low incomes or the disabled scrapping a car, and up to £9,500 for charities, sole traders and small businesses scrapping or retrofitting vans and minibuses.

Home counties residents are not eligible for the initiative.

Mr Khan wrote that London is “in the grip of a deadly public health crisis”, with toxic air “causing the premature deaths of an estimated 4,000 Londoners every year”.

He continued: “It is abundantly clear then that the cost of inaction is far too high and that further action is needed to safeguard public health and spare people unnecessary suffering.

“I’m simply not prepared to stand idly by while toxic fumes from highly polluting vehicles choke our communities and leave our children reaching for inhalers and gasping for air.

“That’s why I’ve chosen to expand the ultra low emission zone London-wide.”

A Government spokesman said: “It’s for the Mayor of London to justify his decision to expand the Ulez, and to properly consult to ensure it is not just a tax on the poorest motorists.

“Decisions on how to allocate funding to best meet the city’s transport priorities are for the Mayor of London to make.

“We have provided TfL (Transport for London) with £6 billion in funding support to keep public transport moving, as well as £2 billion towards vehicle grants and infrastructure to support the rollout of clean vehicles across the country.

“More specifically, London has received almost £102 million of Government funding for projects specifically targeted at helping to tackle pollution.”