Sadiq Khan has suffered a fresh Ulez blow after new figures showed that congestion in London is worse than it was five years ago.

Despite, the Mayor of London's office insisting that the scheme "had already helped reduce traffic in the central zone by approximately 10 per cent", new data suggests congestion levels were 45 per cent last year - up from 37 per cent in 2019.

Research by location tech firm TomTom said it calculated the "congestion level percentage" by comparing the time a driver sat in traffic on a specific journey to the time it would take with free-flowing traffic.

The scheme was implemented to improve air quality across London but an expansion last year to cover all London boroughs has been met with anger.

Andy Marchant, a traffic expert at TomTom said programmes such as Ulez "remain essential to supporting the UK's ambition to reach net zero by 2050".

However, he added: "It should be coupled with long-term action."

"Our analysis shows that five years on from the introduction of ULEZ, London remains the world's slowest city to drive through," Marchant told The Times.

"The capital's fuel consumption and CO2 emissions inevitably increased at the same time, with London's petrol vehicles having the highest CO2 impact in 2023, emitting 3.56 tonnes of CO2 per 10,000 miles driven."

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Experts warn that growing congestion is partly due to a rise in 20mph zones and poor traffic management - even if more vehicles on London roads meet Ulez standards.

According to the TomTom traffic index, London was the slowest city out of 387 globally to drive a six-mile journey last year.

A spokesman for Khan said: "The evidence shows that Ulez is working, with 95 per cent of vehicles seen driving on London’s roads now compliant and don’t need to pay a penny.

"Sadiq has always been clear that the Ulez should not operate in isolation when it comes to tackling dirty emissions.

"That’s why under his leadership London’s transport is now cleaner than ever, with 1,400 zero-emission buses on London’s streets, a third of the UK’s electric charging points and a fivefold increase in protected cycling lanes."

It comes after anti-Ulez protesters clashed with police after campaigners were stopped from demonstrating outside Khan's home on Saturday.

Activists were left furious when officers prevented them from marching near the house in south London.