A team from the University of Bath said the launch of the scheme 15 years ago, and the subsequent introduction of the ultra low emission zone (ULEZ) in 2019, has helped reduce particulate matter (PM10) in Greater London by 13% between 2008 and 2013, compared to 2003 to 2007.

By 2019, nitrogen dioxide levels had fallen by 18.4% in central London, compared to a period between 2016 and 2018.

When comparing London to other cities, such as Manchester, Liverpool or Leeds which do not have similar schemes, researchers said the benefits exceed the implementation costs.

They said the cleaner air contributed to a 4.5% reduction in long-term health problems and an 8% decrease in conditions like asthma and bronchitis, and the clean air zones have generated savings of more than £963m in Greater London.

Research also suggests the LEZ led to a reduction in hospital admissions for respiratory conditions, compared to other areas in England.

Lead author Dr Habtamu Beshir, from the University of Bath, said: "With this analysis, our goal was to offer an objective overview of the impact of low emission zones in the capital and beyond.

"Our study compares London to cities like Manchester, demonstrating the effectiveness of LEZ and ULEZ in improving air quality, enhancing health and alleviating the economic burden of ill health."

Professor Eleonora Fichera acknowledged concerns with compliance costs for owners of older vehicles, particularly affecting poorer communities.

"Our analysis confirms the effectiveness of low emission zones in improving air quality and health - crucial for residents in large cities," she said.

"It shouldn't be a choice between health and affording schemes like ULEZ.

"We must explore innovative policy solutions to make these schemes viable and effective."

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Transport for London said on Tuesday that 95% of vehicles within the city are now compliant with the emission zone requirements. Their figures suggest they receive approximately £730,000 a day in ULEZ fees.

Defending the policy back in August, Sadiq Khan said the expanding ULEZ was a "difficult" but "vital" decision.

The London mayor told Sky News that air pollution causes health issues in children and adults, and also causes 4,000 premature deaths in London per year.