Sir Keir Starmer has backed London mayor Sadiq Khan over his proposal to expand the capital’s charge on the most polluting vehicles.
The Labour leader said Mr Khan “had to take action” due to the legal requirement on him to improve London’s air quality.
Addressing a listener question on LBC, Sir Keir said: “I accept that the mayor has no choice but to go ahead because of the legal obligation on him.”
In November Mr Khan announced his intention to extend the Ultra Low Emission Zone (Ulez) — a scheme originally introduced by Conservative mayor Boris Johnson — to all of London’s boroughs, enlarging it beyond the North and South Circular roads.
If it goes ahead, the extended Ulez will see drivers in outer London pay a £12.50 daily fee from August 29 if their vehicles do not meet the required emissions standards.
The new borders will reach Buckinghamshire, Essex, Hertfordshire, Kent and Surrey.
Conservative-led councils challenged the move in a hearing at the High Court this week and are waiting on Mr Justice Swift’s ruling.
There have been calls from Labour MPs, such as Clive Efford and Jon Cruddas, to delay the expansion and improve its associated scrappage scheme.
Among the party figures to speak out is Danny Beales, who is contesting Mr Johnson’s old seat of Uxbridge and South Ruislip in a by-election on July 20.
Mr Beales reportedly told a recent hustings it was “not the right time” for the charge to be applied more widely.
Sir Keir said it was “right” for the Uxbridge candidate to “stand up” for his potential constituents but argued Mr Khan had been left with no “wriggle room” on the issue.
The Opposition leader said he recognised that the move would cause “pain” and it would be “a lot of money” for motorists to have to pay during the current cost-of-living crisis.
But he said it was “important to make clear” that there was a “legal obligation on the mayor to take measures” in relation to air pollution.
“So he doesn’t just have a free choice to decide what he does here. He has got to take action,” Sir Keir added.
Pressed on whether he supported the call from Labour MPs to delay the rollout, Sir Keir replied: “My experience of the mayor is he always listens to these overtures and that is why he has asked for more money on scrappage.
“I’ve looked at it myself, looked at the legal provision.
“I think it is difficult to say you could simply ignore the legal requirement to do something about this, so the mayor in fairness is between a rock and a hard place on this.”
The former director of public prosecutions suggested Mr Khan would have likely faced legal action from air pollution campaigners if he had opted not to extend Ulez.
Sir Keir said Mr Khan was looking for central government funding to boost the plan for a £110 million scrappage scheme, which is designed to help those who have non-compliant cars or vans.
Following his response, the caller, Tony from Tunbridge Wells in Kent — who described himself as a life-long Labour voter — said he would not be voting for the party at the next election in protest at Ulez.
Mr Khan is looking to become the first politician to be elected London mayor three times at next year’s election, with the Tories in the process of choosing who their candidate will be to rival the former minister.
