More than 4,000 Londoners were hospitalised over the three years because of air pollution.

These figures came from research commissioned by Mayor of London Sadiq Khan, and undertaken by King’s College London and Imperial College London.

The research revealed more than 4,000 people in the capital were taken to hospital between 2014 and 2016 because air pollution worsened their asthma, or in older people, serious lung conditions.

A quarter of those admitted were children under 14 with asthma.

Mr Khan 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.”

It is estimated 600,000 people in London suffer from asthma, including 240,000 children.

Jemima Hartshorn, who founded and runs Brixton-based environmental campaign group Mums For Lungs, which works across the capital, said she was “shocked” but “sadly not surprised by the figures”.

Ms Hartshorn said: “It is frankly unacceptable that these numbers of children are sick from pollution.

“I hope these figures will finally result in Government taking the necessary action and funding councils to deal with this crisis properly.”

The campaigner, who is also a mother-of-two, said she is really worried about what toxic air could do her children’s health.

Ms Hartshorn said: “They might suffer from reduced lung growth, asthma or many of the other illnesses by doing the most natural and essential thing in the world – breathing.”

On April 8 the Ultra Low Emissions Zone (ULEZ) will be introduced in central London in a bid to reduce air pollution in the capital.

This will see people who don’t meet certain emissions standards pay £12.50 to drive in central London.

The ULEZ aims to reduce toxic emissions from transport by around 45 per cent.

Welcoming the ULEZ Ms Hartshorn said: “It is very needed as a first step before the expansion and hopefully a London-wide ULEZ.

“I really hope and believe it will reduce air pollution across London.”