The European Commission, the executive arm of the European Union, said it made a decision to refer Hungary, Italy and Romania to the Court of Justice over persistently high levels of particulate matter.
The European Commissioner for the Environment, Karmenu Vella, said the decision follows through on a threat to the Member States in question that they had received an ample number of final warnings over the last decade to improve the situation.
In January, the nine countries were found to regularly exceed emissions limits set to protect Europeans against particulate matter and nitrogen dioxide (NO2), both pollutants.
However, whilst the government has been keen to highlight that air quality is improving in some parts of the country, the announcement from Brussels has prompted criticism from several corners.
He said: "The news that the European Commission will be taking the UK Government to court for risky levels of air pollution should be a wake-up call".
"It is my belief that today's decision will lead to improvements for citizens on a much quicker timescale".
The NO2 levels were mostly produced by diesel cars and the No 10's plan in 2017 was condemned as as "woefully inadequate" by city leaders and "inexcusable" by doctors. Spain, Slovakia and the Czech Republic dodged that fate for now.
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"The commission had to conclude that... the additional measures proposed are not sufficient to comply with air quality standards as soon as possible", Vella said. But Commissioner Vella emphasised that they are not "off the hook" and the Commission will be monitoring their implementation progress closely. There are no first class and second class citizens: all Europeans have the right to breathe clean air.
Bulgaria and Poland have already been hit with legal action for not keeping to P10 standards.
The European court of justice (ECJ) has the power to impose multimillion euro fines if the countries do not address the problem swiftly.
Julia Poliscanova, clean vehicles and air quality manager at sustainable transport group Transport & Environment (T&E) said the "long-overdue announcement" was a clear message to European Union governments.
The four countries now have two months to reply before further infringement action will be taken.
Especially in Germany, where the auto industry is considered one of the backbones of the country's economy, this decision might cause ripples.
Air pollution from NO2 causes an estimated 23,500 early deaths every year in the UK.
"We can't possibly wait any longer".