The government has made a last-minute application to the high court to delay the publication of its plan to tackle the air pollution crisis.

Ministers were under a court direction to produce tougher draft measures to tackle illegal levels of nitrogen dioxide pollution, which is largely caused by diesel traffic, by 4pm on Monday. The government’s original plans had been dismissed by judges as so poor as to be unlawful.

But following the announcement by Theresa May of a general election on 8 June, ministers lodged a lengthy application to the court late on Friday. It is understood they are asking judges to allow them to breach Monday’s deadline and submit a draft in June – after the election.

It is understood that a full policy will not be produced until September this year.

The government has had months to come up with its air quality plans and Whitehall sources indicated to the Guardian this week they would be published in time.

The late application to delay publication was condemned by the environmental lawyers group ClientEarth, which successfully took the government to court over its air quality plans. MPs have said air pollution in the UK is a public health emergency that causes 40,000 premature deaths a year.

James Thornton, the chief executive of ClientEarth, said: “We are urgently considering the government’s application to delay the publication of the draft air quality plan which was received on Friday evening, less than one working day before the plans are due.

“It is far from acceptable that ministers have left this to the very last minute. The government proposes to delay the publication of the air quality plan despite the clear public health risk caused by illegal air quality. These plans are essential to safeguard public health and they should be put in place without delay.”

The application is likely to be considered by judges on Monday. Judges have already told ministers that their plans were taking too long and imposed the deadline to force the government to come up with new measures more quickly.

The government lodged a lengthy application shortly before 7pm on Friday, which was too late for the court to accept. It will now be considered early next week.

Thornton said the general election was not an acceptable reason to delay taking action against air pollution.

“This is not a political issue but a public health issue. Whichever party is in power, the British public need to see an air quality plan which relies on good scientific evidence and which ensures that people no longer have to breathe toxic air and suffer the grave consequences to their health as a result,” he said.

Anna Jones, from Greenpeace UK also condemned the delaying tactics. She said: “Ministers have had months to come up with a robust plan to tackle illegal air pollution. They have no excuses to delay its publication any further.

“The Cabinet Office guidance makes it clear that essential consultations can still be launched during purdah, and even mentions safeguarding public health as a ground for exceptions.

“Air pollution is a full-blown public health emergency, linked to thousands of premature deaths and a host of health problems. If the government intends to use the election as a pretext to buy more time, that would only be a sign that they just don’t get the gravity of the situation.”

A joint Guardian/Greenpeace investigation revealed this month that hundreds of thousands of children were being educated within 150 metres of a road where levels of nitrogen dioxide from diesel traffic breached legal limits.

A spokesman for the Department for Environment, Food and Rural Affairs said: “We are firmly committed to improving the UK’s air quality and cutting harmful emissions. We are seeking an extension to comply with pre-election propriety rules.”