The UK's highest court has ruled that the government must take immediate action to cut air pollution, a major victory for environment campaigners who started legal action after the country breached EU limits for nitrogen dioxide in the air.
In a unanimous ruling, a panel of five Supreme Court judges, headed by the court's president Lord Neuberger, ordered "that the government must prepare and consult on new air quality plans for submission to the European Commission...No later than December 31, 2015".
NO2 is produced mainly by emissions from diesel vehicles and is linked to a range of respiratory illnesses.
The UK Environment Department said work had already been started on revised plans to meet EU targets on NO2.
The case had been brought by ClientEarth - a group of environmental lawyers - which notes that air pollution causes tens of thousands of premature deaths a year in the UK.
Announcing the decision, Lord Carnwath said: "The new government, whatever its political complexion, should be left in no doubt as to the need for immediate action to address this issue."
ClientEarth lawyer Alan Andrews said: "This ruling will benefit everyone's health but particularly children, older people and those with existing health conditions like asthma and heart and lung conditions.
"The next government, regardless of the political party or parties which take power, is now legally bound to take urgent action on this public health crisis."
A spokesperson for the Department for Environment, Food and Rural Affairs (Defra) said: "Air quality has improved significantly in recent years and as this judgement recognises, work is already underway on revised plans (since February 2014) to meet EU targets on NO2 as soon as possible.
"It has always been the government's position to submit these plans before the end of this year. Meeting NO2 limits is a common challenge across Europe with 17 member states exceeding limits.
