Nine European countries including the UK could face legal action if they fail to make progress on reducing air pollution, the EU's top environment official has warned.

The intervention came as legal air pollution limits for the whole year were reached within a month in London.

Brixton Road, Lambeth, has seen levels of pollutant nitrogen dioxide exceed average hourly limits 18 times so far this year, the maximum allowed under European Union air quality rules.

Inaction by national governments over the issue prompted the European Commission's environment commissioner, Karmenu Vella, to warn of legal action after talks with ministers from nine EU countries including Britain, France, Germany, Spain and Italy - all of which regularly flout the bloc's air quality standards.

"Every year, an astonishing number of citizens' lives are cut short because of air pollution," Mr Vella said.

"We have known this for decades, and the air quality limit values have been in place for almost as long.

"And yet, still today, in 2018, 400 000 people are still dying prematurely every year because of a massive, widespread failure to address the problem."

He continued: "The deadlines for meeting the legal obligations have long elapsed... we can delay no more."

Poor air quality caused by vehicle emissions, industry, power plants and agriculture is known to cause or exacerbate asthma and other respiratory problems.

Air pollution also has significant economic impacts, increasing healthcare costs, reducing employees' productivity and damaging crops, soil, forests and rivers, according to the European Environment Agency's latest annual report.

It has taken the London longer to reach the air pollution limit this year than last year when legal levels were breached less than a week into the new year.

But while campaigners welcomed action by London Mayor Sadiq Khan to tackle pollution, they warned the relative delay in reaching the limit this year could be down to weather conditions dispersing the dirty air.

Environmental groups called for the Government to take urgent steps, including creating and funding clean air zones in pollution hotspots across the UK where 85% of areas still break air quality rules which should have been achieved in 2010.

Government estimates suggest compliance for levels of nitrogen dioxide, much of which comes from road transport, particularly diesel, will not be met until 2026.

The most recent data shows that around 7 per cent of the urban population within the EU was exposed to fine particulate levels higher than the EU-stipulated limit in 2015.

If the stricter World Health Organisation limits are applied, that rises sharply to 82 per cent.

The countries represented at Tuesday's summit have been given ten days to submit new proposals for meeting EU air quality standards regarding particle levels.

In Mr Vella's opinion, the proposals offered by the nine offending countries were "not substantial enough to change the big picture".

He insisted that the only way to avoid court action was to take "all possible measures without delay".

Vella said that at the ministerial meeting some new commitments were given, although he did not specify what they were.

"All those commitments will be evaluated by my services," he said.

"We have also asked the member states that if they have any new measures that they can put on the table, that they have to come with these new measures latest by Monday."

A commission spokesman said however that Monday was not formal legal deadline.

Vella added "there were some positive suggestions but I have to say that at first sight these were not substantial enough to change the bigger picture".

Indeed, it seems unlikely that national governments, which have been aware of the problem for years, would suddenly agree on a new plan in the coming six days.

EU states were required to respect EU-level air quality standards for particulate matter in 2005, and nitrogen dioxide in 2010.

Aside from meeting politicians and making statements, the commission has mainly one tool to make member states comply with the EU air quality standards: the infringement procedure.

The nine countries present on Tuesday are at the receiving end of that procedure, which could end up at the Court of Justice of the EU.

Tuesday's meeting was a political one, outside of the infringement procedure. But Vella stressed that the commission would still go to court if sufficient new measures are not taken.

"There are no new deadlines. We are not delaying, we are not postponing the process. There is a legal process, which is ongoing," he said.

Vella said he reminded ministers that they could be taken to court, but acknowledged that some think that the commission has already waited too long before dragging states to court.

Crucially, the decision to take the final step is not automatic, and needs to be approved by the college of EU commissioners - one from each country.

Vella noted that he would discuss the issue with the college the next day, and had the backing of EU commission chief Jean-Claude Juncker.

Although the start of the infringement procedure has deadlines for member states by which to reply to commission letters, there is no required time limit within which the commission should go from final warning to court.

The commission sent final warnings - so-called 'reasoned opinions' - to Germany, France, Spain, Italy and the United Kingdom on 15 February 2017, almost a year ago.

The Czech Republic already received such a reasoned opinion on 26 March 2015, but almost three years later is still not taken to court.

If the commission does take a country to court, and the court decides that a country has breached EU law, it may receive a fine.

Vella said, when asked about it, that the unique situation of the UK - which is expected to leave the EU in 423 days - was not discussed.

"This was not about Brexit, this was not about the UK," he said.

"We were not addressing the UK specifically, but we were addressing all the ministers that were present there."