Campaigners called for urgent, ambitious action to clean up the UK's air after the High Court rejected a bid by Government to delay publication of plans to tackle illegal pollution.
The Environment Department (Defra) had submitted an application to delay revealing draft plans to reduce illegal levels of nitrogen dioxide, which the court had ordered should be published on Monday April 24, until after the General Election.
But Mr Justice Garnham rejected the bid and said the draft plans must be published on May 9 to allow for any changes following the local government elections which take place on May 4, with the date for the final plan unchanged on July 31.
Dr Penny Woods, chief executive of the British Lung Foundation, said: "The nation's dirty air is one of the most important public health issues in recent times, and the High Court's decision recognises the need to urgently tackle this crisis.
"Toxic air left unchecked will lead to a rising tide of ill health for everyone, particularly those who are most vulnerable. Children, people with a lung condition and the elderly will be hit hardest."
"Government must now deliver ambitious plans to clean up the air we breathe."
Mayor of London, Sadiq Khan, accused Government ministers of having "deliberately used the election as a smokescreen to hold back their plan", instead of taking immediate action to protect the health of the public.
"I hope that after this appalling delay, this Government delivers a strong plan to finally get a grip on this issue and urgently introduces a diesel scrappage fund to rid our streets of the dirtiest cars, and provide financial incentives to encourage people to buy the cleanest vehicles," he said.
Gareth Redmond-King from conservation charity WWF said new research showed how quickly dangerous toxins got into the bloodstream from the air.
"From the remaining coal in in our power stations to the diesel and petrol in our car, bus, van and train engines, we need to ensure dirty fossil fuels are consigned to the dustbin of history," he urged.
Areeba Hamid, clean air campaigner at Greenpeace, said: "Only an ambitious plan will satisfy the public, who for too long have had to suffer exposure to illegal and unsafe levels of air pollution."
"In court, the Government said publishing the air pollution plan would affect the election.
"In reality, air pollution is an election issue with or without publication of this plan, and we clearly need robust commitments from all parties on tackling the UK's toxic air."
There has been speculation the clean air plan could include potentially controversial measures such as charges for motorists to drive diesel vehicles, which cause much of the pollution, in towns and cities, or a diesel scrappage scheme.
Sue Hayman, shadow secretary of state for environment, food and rural affairs, said: "This is the third time that the Government have lost in the courts on the issue of air quality, demonstrating Theresa May's contempt for this most serious of public health issues.
"The Government must now publish their air quality plan without further delay.
"Appealing the decision of the court and creating further delays would be an outrage.
"A Labour government would bring forward a new Clean Air Act, setting out how we would tackle air pollution that NHS experts say contributes to 40,000 premature deaths every year."