Sadiq Khan’s Ulez risks driving up pollution outside the M25, as drivers in London sell their old cars beyond the capital, experts have warned.
Online marketplace Carwow has seen an 68pc increase in customers listing non-compliant cars from London boroughs in recent weeks.
The cars can be picked up at knocked-down prices in the South East and then shipped across the rest of the country, where prices have remained higher and demand for the older vehicles is stronger.
Ian Plummer, commercial director of Auto Trader, said he has been told of retailers snapping up non-compliant cars to sell across the country.
He said: “As the scrappage scheme is capped at £2,000, selling non-Ulez-compliant cars of greater value elsewhere in the country will be the most viable option for many drivers.
“A non-compliant diesel car could be worth anything up to £40,000 so shouldn’t be scrapped, in fact there’ll be high demand for them elsewhere in the country.”
Spencer Gray, who runs Spencer’s Car Sales in Norwich, also said older cars were flooding the used vehicle market as drivers in London try to dispose of non-compliant motors.
Dr Jo Barnes, who runs the Air Quality Management Resource Centre at the University of the West of England, said this could worsen pollution in other parts of the country.
She said: “In other populated areas which don’t have clean air zones there may be a worsening of air quality.
“When we have our own fleet replacement in the UK and in Europe, a lot of those cars go on to secondhand markets in Africa and other parts of the world.
“It’s obviously not going to be a good thing.”
Theresa Villiers, MP for Chipping Barnet on the outskirts of the capital, said she worried that her constituents would struggle to sell non-compliant cars in London.
She said: “So one of the effects of Ulez expansion may just be to move the more polluting cars to other parts of the country.
“This is yet another unintended consequence of the Mayor’s misguided Ulez expansion plans.”
Liberal Democrat candidate for London Mayor, Rob Blackie, said the threat of pollution spread showed that the expansion was “a mess”.
He said: “This yet again proves that not only has the Ulez expansion become a mess, but also that the Government needs to step up by offering proper support for those living on the outskirts of London.
“London isn’t a bubble, people drive in and out every day to work, see their family and shop.”
London’s Ultra Low Emission Zone will be expanded to the whole of Greater London to the boundaries of the M25 from August 29, following a failed legal bid from a number of Greater London councils to stop it.
London Mayor Sadiq Khan was forced to expand the scrappage scheme at the beginning of August, which Transport for London says will ensure the most polluting cars are not resold outside the M25.
Motorists can hand over non-compliant vehicles for scrap and receive payments in return, which can go towards the cost of a new or used low-emission one. Currently, grants go up to £2,000 for a car, £1,000 for a motorcycle, and between £7,000 and £11,500 for minibuses and vans.
A wheelchair-accessible vehicle can garner a scrappage grant of up to £10,000, or £6,000 for a retrofit to make it emit fewer emissions and qualify for an exemption from the charges.
Cabinet ministers were considering using a little-known legal power that allows them to reject a London mayor’s transport strategy if it is “inconsistent with national policies”.
However, The Telegraph understands the formal legal advice commissioned concluded that the move would fail if challenged.
The expansion will mean drivers without a petrol vehicle that complies with Euro 4 emissions standards or a diesel car that complies with Euro 6 rules will be forced to pay £12.50 every day they use their car.
Most diesel cars registered before September 2015 and vans registered before September 2016 are liable alongside most petrol cars registered before 2001.
A Transport for London spokesman said the expansion of the “very targeted” Ulez scheme was expected to reduce emissions by more than 5pc.
“To date, almost 13,000 applications for scrappage grants have been approved and more than £52m has already been committed to Londoners and London’s small businesses and charities,” the spokesman said.
They added the scrappage scheme would “ensure the most polluting vehicles are removed from our streets and not sold elsewhere in the UK”.