The government has warned two councils of “serious consequences” after they failed to meet the deadline for dealing with air pollution.

In 2015, five local authorities with some of the worst pollution outside London – Derby, Southampton, Leeds, Nottingham and Birmingham – were ordered to produce proposals to tackle air pollution by 15 September.

After it emerged this week that Derby and Southampton were likely to miss the deadline, the environment minister wrote to them saying they must deliver plans to ensure nitrogen dioxide compliance is achieved quickly.

Thérèse Coffey told the councils: “You will … wish to consider the risks of missing the legal deadline and the serious associated consequences. I am very clear that local authorities must deliver plans so that nitrogen dioxide compliance is achieved as quickly as possible.”

However, Greenpeace said ministers were in no position to “shake their fists” at cash-strapped councils.

“While it is right that local authorities are being reminded to play their part in tackling air pollution, the government’s message would carry far more weight if ministers had practised what they were preaching,” it said. “Instead, they failed to rein in illegal air pollution for years … and are still delaying the measures we need to clean up our air.”

The government has lost three court cases over air quality since 2015. Each time its plans to tackle the problem were deemed to be so inadequate as to be unlawful.

The government has also been criticised by campaigners and MPs for its slow response to the issue. ClientEarth, a legal campaign group that successfully sued the government over its clean air proposals, said people in the UK were being forced to breathe “illegally dirty air”.

Its lawyer, Katherine Nield, said air pollution was “a serious national problem which needs national-scale solutions, coordinated by central government”.

She said the government had placed the onus on local authorities, and was now chasing them up “at the 11th hour” for potentially missing deadlines. “This gives us very little faith that passing the buck to local authorities in this way will be able to clean up our air with the urgency we need.”

In the government’s 2015 air quality plan, the five councils were told to investigate whether establishing clean air zones or alternative measures would best tackle illegal levels of pollution.

At the time, the government was criticised for asking local authorities to accept responsibility for decisions that were likely to be unpopular with motorists.

Chris Poulter, the leader of Derby council, said the local authority acknowledged Coffey’s comments and concerns and it was preparing a response, which would be posted on its website.

He added: “The current administration carried out an urgent review on the council’s position on air quality, in particular, nitrogen dioxide issues. Council officers are working to this agenda, and are making significant progress … We are working hard to submit a full business case to government by the end of the year.”

Christopher Hammond, the leader of Southampton city council, said many of the issues were not within its control. “We have acted in good faith to satisfy government expectations. Shifting goalposts have left us playing catch-up on an issue that is of great importance to local communities in Southampton, including the business community,” he said.

“We have advised [the government’s joint air-quality unit] of the various issues that are preventing us from submitting a robust plan by 15September … It is our view that the risk of legal challenge is more likely to delay delivery of improvements rather than missing the immediate deadline set by government.”

At least 40,000 people die each year because of the UK’s air pollution crisis, with 9,000 of those in London. It is known to be a major risk factor for childhood asthma and other respiratory conditions and there is growing evidence linking toxic air to a range of otherserious conditions, from heart disease to dementia.

ClientEarth said the government had a legal and moral duty to protect people from dirty air. “Central government itself needs to deliver countrywide policies, like a national network of clean air zones, to bring air pollution down at speed,” Nield said.

The Department for Environment, Food and Rural Affairs said: “Tackling air pollution requires collective action, which is why we are working with towns and cities to improve local air quality.

“We have published a £3.5bn plan to reduce harmful emissions and our ambitious new clean air strategy has been welcomed by the World Health Organization.



“While we have given local authorities technical support in developing their plans, and nearly £500m in funding for air quality improvements, local leaders are best placed to determine the best approach to rapidly meet the needs of their communities.”