The European Commission says it will refer the UK to the Court of Justice of the European Union for its failure to address air pollution.
It is one of six countries being referred for air quality infringements. France, Germany, Hungary, Italy and Romania have also been referred.
The Czech Republic, Slovakia and Spain were also facing infringement proceedings – these remain open, but for now, they have not been referred to the Court of Justice of the EU.
Client Earth CEO James Thornton said: “The European Commission’s action, which could end with the UK having to pay fines, should be another strong catalyst for ministers who have failed for almost a decade to take the necessary action.
“The UK needs a new Clean Air Act fit for the 21st Century and targeted action, like scrappage schemes and clean air zones which keep the dirtiest vehicles out of our most polluted towns and cities.
“We need an overhaul of fiscal incentives to favour cleaner ways of getting around and we need the car industry to contribute financially to help get us out of the mess that it helped create.”
ClientEarth has taken court action against the UK government on three occasions over air quality. A supplement to the national Air Quality Plan is currently being formulated by the government.