London has introduced one of the world’s toughest vehicle emissions standards.

Drivers of older, more polluting cars face paying a new £12.50 fee to enter the centre of the capital after the ultra-low emission zone (Ulez) came into force on Monday.

Diesel cars must be less than roughly four years old to avoid the charge, while petrol cars must be less than about 13 years old.

London mayor Sadiq Khan said the scheme is being brought in because thousands of Londoners are dying early every year as a result of toxic air, with an increased risk of cancer, asthma, dementia and stroke.

He claimed the Ulez will “help clean our air and reduce harmful road transport emissions”.

Mr Khan commissioned a study by King’s College London and Imperial College London which found that poor air quality leads to about 1,000 London hospital admissions for asthma and serious lung conditions every year.

He said: “As someone who developed adult-onset asthma over the last few years, I know from personal experience that London’s toxic air is damaging people’s health.

“This study is a stark reminder that air pollution disproportionately affects the most vulnerable Londoners and I’m doing everything in my power to protect children, the elderly and those with respiratory conditions from our filthy air.”

The Ulez initially covers the same area as the congestion charge zone, but will be extended to the whole of inner London within the North and South Circular roads from October 2021.

Charges apply at all times and are on top of the congestion charge, which is £11.50 between 7am and 6pm on weekdays.

All vehicle types apart from black taxis are liable for the Ulez charge unless they meet certain emissions standards or exemptions.

Non-compliant lorries, buses and coaches face a £100 daily fee.

It is estimated that 100,000 cars, 35,000 vans and 3,000 lorries may be affected every day once the zone is expanded.

City Hall believes thousands of drivers have upgraded to newer, cleaner vehicles or changed their journey patterns ahead of the introduction of the Ulez.

Its figures show the proportion of vehicles not compliant with the required emissions standards fell from 61% in February 2017 to 39% last month.

The Ulez was announced by former London mayor Boris Johnson, but his successor Mr Khan brought its start date forward and decided on the 2021 extension.

There has been concern that poorer motorists, small businesses and charities will be unfairly hit by the charge as they are less able to afford to upgrade their vehicles.

London director of business organisation the CBI, Eddie Curzon, described the Ulez as a “really positive step” but warned that “smaller firms can struggle to afford the switch to low-emission vehicles”.

He said: “To make a success of the Ulez, it is crucial that City Hall works with firms to help them take advantage of new technologies and support them, where required, to accelerate the take-up of low emission vehicles.”

Greater London Authority Conservative group leader Gareth Bacon claimed Mr Khan’s decision to bring forward the initiative by a year has “caught small businesses and charities on the hop”.

He added: “The damage caused by the early introduction of the central Ulez will pale into insignificance compared to the impact of its extension to the North and South Circulars in 2021.

“This punitive move will hit the very poorest Londoners hardest.”

City Hall said Transport for London is running a scrappage scheme to help the smallest businesses and charities switch to cleaner vehicles.

It also noted that people in London’s most deprived areas are more likely to suffer from poor air quality and are least likely to own a car.