LONDON - Hundreds of thousands of children are being exposed to illegal levels of air pollution from diesel vehicles at schools and nurseries across England and Wales, a joint investigation by the Guardian and Greenpeace's investigations unit has revealed.

The analysis of the most recent government data shows how dangerous levels of nitrogen dioxide (NO2) pollution from diesel traffic are not limited to large metropolitan centres, but also found in towns and cities from Newcastle to Plymouth, the Guardian reported on Tuesday (April 4).

More than 1,000 nurseries which look after 47,000 babies and children are in close proximity to roads where the level of NO2 from diesel traffic exceeds the legal limit of 40µg/m3, (micrograms per cubic metre of air).

The findings come as the government is under pressure to dramatically improve its strategy to clean up the nation's air, after the high court said its plans to reduce illegal levels of harmful emissions were so poor as to be unlawful.

Ministers have to produce new draft measures to tackle air pollution by April 24.

Chris Griffiths, professor of primary care and public health at Bart's and the London School of Medicine, said the findings were very important and called for a dramatic change in attitudes within society and from government.

"The research on exposure to traffic fumes and children's lung growth is pretty consistent. It shows that such exposure reduces lung growth, produces long term ill health and can cause premature death. We should be outraged that we are exposing our developing children to these obvious problems."

The investigation used the government's own pollution modelling from 2015 to identify all schools and nurseries - whether private, academy or state maintained - which are within 150 metres of a road where emissions of NO2 are above the legal limit, reported the Guardian.

The findings: Birmingham was the worst area outside London for children's exposure to diesel traffic fumes, said the report. Thirty-eight nurseries and 30 schools in the city are within 150m of a road where emissions of nitrogen dioxide exceed the legal limit.

Smaller towns and cities - including Poole and Oxford - also suffer diesel traffic pollution problems, said the Guardian. In the south-west coastal city of Plymouth nearly 10 per cent of nurseries are within 150m of illegal levels of NO2 emissions from roads.

Anna Jones, clean air campaigner at Greenpeace, said there was a need to raise awareness around the country about dangerous levels of NO2 air pollution. She called for urgent government action with car companies to get polluting vehicles off the streets.

"Most people don't realise that all across the country toddlers are being exposed to invisible air pollution caused by diesel vehicles," said Jones.

"We were told diesel vehicles were the cleaner choice but car makers lied about the toxic pollution they emit."

Britain has been in breach of European Union air-quality regulations since 2010, with diesel shouldering part of the blame, reported Bloomberg.

Governments across Europe encouraged the growth of diesel in the first decade of the century because burning the fuel emitted fewer greenhouse gases than petrol because of its greater efficiency.

British Prime Minister Theresa May said on Tuesday plans to tackle air pollution will need to be mindful of the fact that previous governments encouraged people to buy diesel vehicles.

"I'm very conscious of the fact that past governments have encouraged people to buy diesel cars and we need to take that into account when we're looking at what we do in the future,'' May told reporters during a three-day visit to Jordan and Saudi Arabia, Bloomberg reported.

London Mayor Sadiq Khan said on Tuesday he plans to impose a new 12.5-pound charge on the most polluting vehicles, on top of an existing congestion charge, starting in April 2019.

The fee will bring the total daily charge to 24 pounds for petrol-burning cars that are around 13 years old or more, and diesel cars that are at least four years old.