The environmental lawyers won both cases against ministers previously.
ClientEarth’s grounds for the latest judicial review are that the air quality plan “backtracks on previous commitments to order five cities to introduce clean air zones by 2020 and it doesn’t require any action in 45 local authorities in England despite them having illegal levels of pollution.
It adds the plan also does not require action by Wales to bring down air pollution as quickly as possible.
James Thornton, ClientEarth CEO said: “The UK Government’s stubborn failure to tackle illegal and harmful levels of pollution in this country means that we have no choice but to take legal action. We need clarity from the government and for that we’ve been forced to go back to court.”
The Department for Environment, Food & Rural Affairs (Defra) said it cannot comment on ongoing legal proceedings.
A spokesperson added: “We have put in place a £3 billion plan to improve air quality and reduce harmful emissions. We will also end the sale of new diesel and petrol cars by 2040, and next year we will publish a comprehensive Clean Air Strategy which will set out further steps to tackle air pollution.
“We now have an opportunity to deliver a green Brexit and improve environmental standards as we leave the EU.”