The Telegraph newspaper reported on Saturday that London Mayor Sadiq Khan's office tried to "silence" scientists who called into question the effectiveness of the ultra-low emissions zone (ULEZ) policy promoted by the head of the city.

The newspaper claimed that Shirley Rodrigues, the London Mayor’s deputy for environment and energy, told in emails sent in November 2021 to Imperial College London professor Frank Kelly that she was "really disappointed" by scientists publishing results that cast doubt on the effectiveness of ULEZ.

In particular, Rodrigues said that she was "deeply concerned" about the damage done to the credibility of the Mayor’s office and ULEZ. In response, Kelly promised to write a ULEZ-friendly report, the report indicated.

Kelly sent a statement to Rodrigues to check, which initially said actions by the Mayor were "collectively providing a major benefit to the city." She replied, crossing out the word "collectively" and she added that the Mayor’s schemes "have dramatically reduced air pollution in London."

The Telegraph revealed that since 2021, Kelly's research group has received over 800,000 pounds ($1.018 million) from the mayor's office. But the publication by scientists led to a cooling in their relations with the London city hall, which, in turn, caused the reluctance of representatives of the scientific community to write any new materials about ULEZ, the newspaper pointed out.

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The emails also show that, on February 14, 2023, the Greater London Authority (GLA) asked Kelly to complain about a Telegraph article reporting on the uncertainty of air pollution death figures widely cited by the London Mayor, based on Kelly's research.

The GLA offered to set up a "friendly interview" for him with "very supportive" David Lammy, the Labour MP for Tottenham. 

At the time, Kelly warned that "Imperial’s press office is not keen for us to put a direct contradiction to the Telegraph article" but said that "as always, I’m happy to fight back." He also asked the Mayor’s office to provide him with "a form of words" with which he could challenge the article.

On April 17, Kelly admitted on the Evening Standard’s The Leader podcast that his research, paid for by the Mayor, would provide Khan with "useful ammunition" to promote his ULEZ expansion.

The ULEZ initiative was first announced by then-Mayor of London Boris Johnson in 2015, with the aim of improving air quality by reducing the number of vehicles in London that don't meet emissions standards. Later, Khan launched an initiative that included, among other things, the installation of special traffic signs and cameras.

The scheme requires the most polluting vehicles to pay a £12.50 ($16) toll on days they are driven within the inner city.

Paul Osborn, the leader of Harrow Council, which is resisting the ULEZ expansion, said that "These dodgy emails raise important questions about the scientific basis for extending the ULEZ. I have long believed that this expansion will have a very limited impact on air pollution but comes at a massive cost to the poorest and most vulnerable motorists."

Petrol cars registered pre-2006 and diesel vehicles first registered before September 2015 are unlikely to meet the minimum emissions standards required.

Its extension to all of Greater London later this month has prompted a fierce backlash from many living in and around the newly encompassed areas, who face fines of up to £160 for each day they fail to pay.

Khan, 52, insists the wider ULEZ will help improve London's "toxic air pollution," which causes thousands of annual deaths and life-changing illnesses. He developed adult-onset asthma nine years ago and blames it on decades of breathing the capital's poor air.

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