The Ultra Low Emission Zone (ULEZ) has come into force in central London.

Drivers of older, more polluting vehicles are being charged to enter the congestion zone area at any time.

Transport for London (TfL) hopes the move will reduce the number of polluting cars in the capital, and estimates that about 40,000 vehicles will be affected every day.

Mayor of London Sadiq Khan said it was “important we make progress” in tackling the capital’s toxic air.

Jemima Hartshorn, founder of clean air campaign Mums for Lungs, said: “The ULEZ is a fantastic first step forward to tackling London’s dirty air.”

Most vehicles which are not compliant will have to pay £12.50 for entering the area each day, in addition to the congestion charge.

Vehicles can be checked using TfL’s online checker but broadly speaking, those which are non-compliant are:

• motorbikes that do not meet Euro 3 standards (pre-2007 vehicles)
• petrol cars and vans that do not meet Euro 4 standards (vehicles pre-2006)
• diesel cars and vans that do not meet Euro 6 standards (vehicles pre-2015)
• Buses, coaches and lorries will need to meet or exceed the Euro 6 standards or pay £100 a day

Anybody who does not pay the charge will face a fine of £160, although a first offence may result in only a warning letter.

The ULEZ is set to be expanded to cover the entire area between the North and South Circular roads in 2021.

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TfL estimates the initial scheme will lead to a reduction in toxic emissions from road transport by about 45% in two years.

Mr Khan said London’s air pollution was a “public health emergency” and it was the “poorest Londoners that suffer the worst quality air”.

Figures from City Hall show that more than 60% of all vehicles driving through charging zone in March were already compliant with the new restrictions.

Nearly 27,000 non-compliant vehicles have been taken off of the roads in the last two months, resulting in the total number of cars entering central London drop by 11%.

However, the Federation of Small Businesses (FSB) said many small firms were “very worried about the future of their businesses” as a result of the “additional cost burden”.

Some drivers have also spoken about their anger that governments had previously recommended buying diesel cars which are now being targeted in particular by the charge.

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Go Ultra Low, an electric vehicle campaign backed by the government, said: “There has never been a better time for drivers to consider making the switch to electric.

“ULEZ and congestion charge exemptions for electric cars meant “switching can not only save money, but also help make a difference to local air quality.”