Theresa May’s visit to India will decrease her lifespan by several hours due to the heavy air pollution in the city's capital, experts have said.

The Prime Minister’s three-day trade mission to Delhi will have exposed her to air that is 36 times more toxic than London, according to an analysis commissioned by Greenpeace's Energydesk.

The Indian capital has been experiencing one of the worst air pollution episodes in its history in recent weeks, after Diwali celebrations enveloped the city in a deep smog made up of smoke, ash and other pollutants.

Cambridge University statistician David Spiegelhalter told Energydesk the Prime Minister's exposure to the such air pollution levels could knock hours off her life.

Data downloaded by Greenpeace India from the Central Pollution Control Board shows the average measurements for the particulate PM 2.5 in Delhi over the three days of Ms May's visit was 552 μg/m3 - compared to an average reading of 15 μg/m3 in London.

In light of the findings, Greenpeace urged that while air pollution in India was a pertinent issue, Ms May must take action to tackle the “illegal levels of air pollution” in the UK.

Anna Jones, Greenpeace Air Pollution campaigner, said: “Theresa May, like all the citizens of Delhi, is experiencing a very extreme example of air pollution right now. But back home in the UK, people are also experiencing illegal levels of air pollution that is having a huge impact on our health.

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“It's more invisible and the numbers may be lower – but the levels are by no means safe. When she gets home, May must act to phase out diesel vehicles in order to give us all the right to breathe clean air.”

It comes less than a week after Theresa May promised new air pollution policies following a High Court ruling that the her government was not doing enough to tackle the problem in the UK.

The Prime Minister's promise followed heavy criticism after the ruling, with environmental legal group ClientEarth condemning it as a “damning indictment of ministers’ inaction on killer air pollution”.