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Buckingham Palace suffers from the highest level of air pollution in the country with almost four times the European legal limit, according to the latest figures.

Grosvenor Place, which runs alongside the Queen’s London residence, had the highest level of the toxic gas nitrogen dioxide in 2012.

Researchers found 152 milligrams of the gas per cubic metre of air, with a main contributor being diesel engine fumes. The EU legal limit is 40.

Figures released by DEFRA following a freedom of information request reveal all 50 of Britain’s pollution blackspots are in the capital.

Other highly polluted areas include Oxford Street near Marble Arch, which registered at 150 micrograms, and Cockspur Street near Trafalgar Square on 138 micrograms.

The fourth and fifth locations were Park Lane and Knightsbridge - which measured 135 and 134 micrograms respectively.

Roads near other top London tourist attractions such as Madam Tussauds, Hamleys Toy Shop and Covent Garden also featured on the list of 50 worst offenders.

The gas can lead to respiratory disease and can cause the lining of the lungs to become inflamed.

The government is the subject of legal action after failing to deal with the high level of the toxic gas in the country’s cities.

Simon Birkett, Founder and Director of Clean Air in London, said: “These levels of nitrogen dioxide (NO2) are nothing short of staggering.

“The thought that hundreds of thousands or millions of tourists and Londoners in a year may be exposed to air pollution this high is deeply troubling.”

The UK faces fines of up to £300m from the European commission for failing to reduce high levels of NO2 air pollution from traffic.

A spokesman for Boris Johnson said said: “Since the Mayor was elected, NO2 emissions have reduced by 20 per cent and the number of people living in areas exceeding NO2 limits has halved but he fully recognises the need to take further action.

“This includes the introduction of the world’s first Ultra-Low Emission Zone in central London from 2020, tougher requirements for taxis from 2018 and a £20million fund to tackle local problem areas.

“These most ambitious measures will deliver enormous economic and environmental benefits for central London and will make this global city an even better place to live, work and visit.”