A London mother campaigning for stronger action on air pollution has said plans to expand the Ultra Low Emission Zone (ULEZ) had become a "political football".
Rosamund Adoo-Kissi-Debrah's daughter Ella died aged nine in 2013 - partly due to the effects of pollution.
She supports the Labour mayor of London's plans to extend the scheme across the whole of the capital.
But Labour's leader has said Sadiq Khan should "reflect" on the proposals.
The expansion of the scheme, due to be enforced from the end of August, would mean drivers of the most polluting cars will have to pay Â£12.50 a day to drive in any part of Greater London.
Sir Keir Starmer has blamed the plans for the party's loss at the recent by-election in Uxbridge and South Ruislip, a seat made vacant by the former Conservative prime minister Boris Johnson.
Mr Khan has defended his plan as "the right one".
The scheme has been strongly opposed by motoring groups and some councils. Five Conservative councils have brought a judicial review of the plans to London's High Court. A judge is expected to make a ruling in the coming weeks.
Ms Adoo-Kissi-Debrah, who has campaigned for tougher legislation to cut pollution told the BBC on Monday: "We should this morning be talking about children and the most vulnerable and this has now turned in to a political football".
Ella, from Lewisham, south-east London, was the first person in the UK to have air pollution listed by a coroner as a cause of death.
She was found to have been exposed to "excessive levels" of toxic air near her home.
"The coroner was very clear that everyone needs to work together - the Department of Heath, transport, the environment, the mayor of London's office and all councils," Ms Adoo-Kissi-Debrah said.
After Labour's loss at the Uxbridge by-election, Sir Keir said ULEZ was "the reason we didn't win there" adding, "we've all got to reflect on that, including the mayor".
He said he had spoken to Sadiq Khan, but declined to say whether he believed the ULEZ expansion should be paused or scrapped.
Sources close to Mr Khan told the BBC he was in "constructive listening mode" but added that he had no plans to delay the scheme's expansion at the end of August.
In the decade since her daughter's death, Ms Adoo-Kissi-Debrah has campaigned for a new law.
"Mr Khan is legally obligated to clean up the air and so is the government," she told Radio 4's Today programme.
'People want clean air'
When asked whether she was seeing Labour's commitment to cleaning up the air "wavering", she said: "I am".
"We should be talking about different ways to mitigate ULEZ, that is what we should be discussing. People do want clean air."
Sir Kier Starmer said on Friday: "When it comes to green commitments, it's not a question of whether they should be done, of course it needs to be done - it's how they're done."
Ms Adoo-Kissi-Debrah also said she had told Ed Miliband, the shadow secretary of state for Net Zero, she did not think a planned new anti pollution law would ever be introduced.
If it were to become law, The Clean Air Bill would force the government to act to bring air quality to minimum standards set by the World Health Organization, which are stricter than the UK's current standards.
It has so far had two readings in the House of Commons.