Sir Sadiq Khan's officials concealed taxpayer-funded research indicating that low-traffic neighbourhoods (LTNs) do not lead to a reduction in car usage, it has been revealed.
Transport for London (TfL), which Mr Khan chairs, reportedly chose not to publish the study after academics found the LTNs do not push people not to drive.
London City Hall Conservatives' transport spokesman, Keith Prince AM, accused the Labour Mayor of overseeing a "cover-up", urging Sir Sadiq to "correct the record".
LTNs are road-blocking schemes, initially introduced by the Tories during the Covid lockdowns.
They physically close residential streets by using large obstructions.
Gaps are left in those blockades so pedestrians and cyclists can get through, with politicians hoping it reduces people's ability to drive.
Sir Sadiq was knighted for his "political services" earlier this year and has repeatedly claimed that LTNs reduce road traffic.
In 2021, he said that the "main benefit of LTNs is to reduce short journeys by car" and in 2022, he claimed that the scheme was "effective in reducing car use".
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Sir Sadiq said LTNs are 'effective in reducing car use'
| PAA study from the University of Westminster has found that LTNs do not have "a significant effect associated with car use".
In an email seen by The Times, an official reminded others that "all of this stuff is FOI-able" (available under freedom of information laws), before stating that no one outside TfL knew about the study.
Professor Rachel Aldred was one of three authors on the report and is a former trustee of the pro-LTN London Cycling Campaign.
One of the authors suggested creating a "suitably contextualised and caveated summary" of the study for publication by TfL.
Mr Prince said: "Sadiq Khan has spent years telling us LTNs cut traffic use and now it turns out covered-up data suggests otherwise. He needs to correct the record immediately.
"The mayor is the chair of the TfL board. He needs to come clean on whether he ordered this cover-up."
The spokesman called for Sir Sadiq to conduct a "full investigation so he can tell Londoners exactly who did", if the Mayor did not cover up the data.
He continued: "If it was, in fact, his decision, then Londoners will rightly see that as an utter disgrace."
Sir Sadiq has been ordered 'to come clean on whether he ordered this cover-up'
| PAThe London Mayor has recently been outspoken about US President Donald Trump during his second state visit, saying he is fanning "the flames of the far-right".
Sir Sadiq said: "A toxic form of politics is spilling out onto our streets. These are dark times, but those who seek to divide us will not win."
At the President's first state visit, he described Mr Khan as "a nasty person" who has "done a terrible job".
Despite being openly critical of the Mayor, Mr Trump said he would "certainly" visit London.