The London Assembly has called on Sadiq Khan to consider using emergency powers to allow Oxford Street to go ahead despite Westminster City Council (WCC) scrapping it last month.
The council pulled the plug on the mayor's flagship policy last week citing concerns the scheme did not have a "strong democratic mandate" for residents, some of whom had complained about the noise created by diverted bus routes.
The London Assembly today agreed a motion calling on Khan to consider using powers within the Greater London Authority Act (GLA) 1999 to pursue the pedestrianisation scheme if needed.
Assembly member Caroline Russell said: "The backsliding on plans for Oxford Street is really disappointing. London's main shopping street mustn't be left clogged with pollution and vehicles – a less and less pleasant place to go.
"All the studies show that pedestrianisation actually helps shops by creating a public space where people can browse, hang out with friends and get around safely and comfortably.
"The Mayor already has legal powers to fulfil his manifesto pledge of transforming Oxford Street. He should use them".
Florence Eshalomi who seconded the motion, said the GLA would enable the mayor to take over any road in London with the consent of the borough or the government. "If Westminster Council remains unwilling to come back to the table, the mayor should use this power to urgently remove the toxic air-polluting vehicles from Oxford Street," she said.
Caroline Pidgeon, the sole Liberal Democrat member of the Assembly and chair of the Transport Committee at City Hall, said Oxford Street would "quite frankly die" as a global destination for shopping if it did not adapt.
“A destination with such a high number of road casualties, crowded pavements for pedestrians and illegal levels of air pollution has no real future," she said.
“We also cannot overlook the reality that with Crossrail the crowded pavements of Oxford Street will become even more unpleasant.
“It is time to get real and grasp the huge opportunities that pedestrianisation can bring.”
Yesterday Khan wrote to the council warning it that any alternatives it puts forward will need to tackle certain challenges or he won't commit funding to them.
Khan said £8m had already been invested in the abandoned project, and that Londoners would expect him to be "mindful" of this in taking future decisions about investment in Westminster.
The council is due to meet next week to consider a report setting out the next steps for transforming the Oxford Street district. It was looking to plug £727,000 – made up of a reallocation of £327,000 of the council's own revenue, and £400,000 from the local implementation plan allocation – into the pedestrianisation alternative.