The British government has failed in a legal bid to delay the publication of its plan to tackle air pollution until after the general election on June 8.
The government had gone to the High Court to extend an April 24 deadline to submit its plan to improve air quality and comply with nitrogen dioxide limits set by the European Union (EU).
But the court ruled on Thursday against any extension, ordering a draft plan to be submitted by May 9 and a full report by July 31, British media reported.
The government is obliged to draw up a new plan after the High Court ruled in November that a calculation of future vehicle emissions was too optimistic.
It was not immediately clear whether the government would appeal Thursday's ruling.
The Department for Environment, Food and Rural Affairs said it was considering the judgment.
Concern over air quality has grown since the Volkswagen emissions scandal broke and reports that real-world emissions exceed those recorded during laboratory tests have put pollution high on the political agenda.
"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," said Areeba Hamid, a clean air campaigner at environmental group Greenpeace.
Nitrogen oxides reduce air quality and EU member states have been flouting limits on a range of pollutants associated with respiratory and other illnesses and more than 400,000 premature deaths per year, according to European Commission data.
Under the EU's Air Quality Directive, member states were supposed to comply with nitrogen dioxide limits in 2010 - or by 2015 if they delivered plans to deal with high levels of the gas, which is produced mainly by diesel engines.