Britain is one of six countries facing the possibility of fines running into the millions over the problem of toxic air.
Along with France, Germany, Italy, Hungary and Romania, the UK was referred to the European Court of Justice by the European Commission after it breached EU air quality rules.
Nitrogen dioxide (NO2) levels, peaked at 102 microgrammes per cubic metre of air in 16 locations including London in 2016 – more than twice the EU limit of 40 microgrammes.
Air pollution is estimated to cause 9,500 deaths each year in London alone, according to a King’s College London study, and 40,000 early deaths a year across the UK.
The European Commission also issued a letter of formal notice to the UK for disregarding EU measures to deter car manufacturers from trying to cheat emissions tests, introduced in the wake of the Volkswagen diesel scandal.
The EU’s environment commissioner Karmenu Vella said: “The decision to refer member states to the Court of Justice of the EU has been taken on behalf of Europeans.
“We have said that this Commission is one that protects. Our decision follows through on that claim.
“The member states referred to the Court today have received sufficient ‘last chances’ over the last decade to improve the situation.
“It is my conviction that today’s decision will lead to improvements for citizens on a much quicker timescale.”
The Department for Environment, Food and Rural Affairs (Defra) said the UK was one of 22 EU states exceeding NO2 limits.
It said the main reason for non-compliance was the failure of European standards for diesel cars to deliver the expected reductions in emissions.
A Defra spokesman said: “We continue to meet EU air quality limits for all pollutants apart from nitrogen dioxide, and data shows we are improving thanks to our efforts to bring levels of NO2 down.
“We will shortly build on our £3.5 billion plan to tackle roadside emissions with a comprehensive Clean Air Strategy setting out a wide range of actions to reduce pollution from all sources.”
Green Party co-leader Caroline Lucas welcomed the Commission action.
“This announcement is good news for all those suffering from chronic air pollution,” said Ms Lucas.
“People have been breathing in toxic air for too long because of the failure of the British Government in tackling this issue.”