The data, which suggests that three of Britain’s cities – London, Birmingham and Leeds – will exceed the European air pollution limits, was published on the Defra website yesterday (10th July) and comes as the UK faces legal action for its failure to meet the legal limits.

Lawyers from the EU Commission said this would be ‘perhaps the longest running infringement of EU law in history’.

Alan Andrews, from environmental law firm ClientEarth, which has brought a case against the UK for the breach, said: ‘It’s bad enough that the Government has no intention of complying with these limits in the foreseeable future.

‘It’s even worse that they’re trying to hide behind legal procedural rules to keep this quiet. We have a right to breathe clean air and the right to know when the government is failing to protect us.’

He added: ‘Another five years of delay means thousands more people will die or be made seriously ill. The UK needs to act now to get deadly diesel vehicles out of our towns and cities.’

Air pollution causes 29,000 early deaths a year in the UK whilst the World Health Organisation has previously said that air pollution causes cancer. Current scientific evidence has also linked nitrogen dioxide with adverse respiratory effects including airway inflammation in healthy people and increased respiratory symptoms in people with asthma.

Friends of the Earth air pollution campaigner Jenny Bates said: ‘Failure to meet air pollution limits in three of our major cities for another 16 years would have serious impacts on the health of thousands of people.

‘These air quality rules should already have been met. Government, councils and the London Mayor must make this issue an urgent priority, and end this national scandal.

‘Rapid steps to ban the dirtiest vehicles and cut traffic levels must be taken, and road-building plans that will simply add to the problem should be abandoned.’

A Defra spokesperson responded: ‘We are investing heavily in measures to improve air quality and have committed billions to increase uptake of ultra-low-emission vehicles, sustainable travel and green transport initiatives.

‘As our understanding of NO2 evolves this must be reflected in our projections which is why we have revised these figures – work is under way to ensure compliance with EU limits in the shortest possible time.’