The Greens have accused Sadiq Khan of contradicting himself over plans to expand London City Airport.
The current Mayor of London effectively ditched City Hall’s objection to the expansion project shortly after his election earlier this year.
But this week, in a written answer to a question from Green Assembly Member Caroline Russell, he suggested further airport expansion in the capital would not be compatible with clean air targets.
Khan wrote that he was “not persuaded further expansion of airports within London would be compatible with my aim of achieving legal limits for air quality as soon as possible”.
Russell said Mayor Khan was sending “mixed signals”.
She added: “While it’s welcome news that the Mayor recognises that further airport expansion will make it impossible to end the illegal levels of air pollution across London, many people will be confused about why he removed City Hall’s objection to the City Airport expansion back in May.
“The Mayor should stand up for the people of East London, who are set to be blighted by even more air pollution and aircraft noise, stop sending mixed messages and say he’s against the expansion of City Airport if it means that his air pollution plans will be in tatters.”
Mayor Khan’s spokesman denied he was sending mixed messages, emphasising that central government had approved London City Airport’s planning application without various protections that both he and his predecessor Boris Johnson had sought.
In his answer to Russell’s question, Khan wrote that, now expansion had been approved, “we need to ensure air quality will not be adversely affected”.
He added: “I am therefore glad measures will be put in place by the airport, should it expand, such as the provision of electric power to reduce aircraft engine use on the ground and improvements in the ground vehicles at the airport.
“There will also be extensive monitoring undertaken and if the airport does not deliver on its commitments not to worsen air pollution I will hold them to account.”
John Stewart from HACAN East, a campaign group that is opposed to airport expansion, said: “In an ideal world we would like to have seen the Mayor oppose the plans but now that they are going ahead, we are keen that he backs our call that London City looks again at its plans to concentrate all its flight paths.
“It simply means particular communities get all the planes. And expansion will make it even worse.”
Declan Collier, the chief executive of London City Airport, has previously said: “Expansion at London City Airport will create more than 2,000 new jobs in East London, add much-needed aviation capacity in the South East, and generate an additional £750m per year for the UK economy.”