Campaigners are going back to the High Court to challenge the government's plans to improve air quality.
In May, draft measures on reducing nitrogen dioxide levels in the UK were published after a judge ruled that existing plans to meet EU-mandated air quality limits were inadequate and must be improved.
On Wednesday in London, ClientEarth will argue that the draft sets out no evidence of any plans for concrete actions in Scotland, Wales and Northern Ireland, and that the plan for England is fundamentally flawed.
The environmental law organisation claims this is a breach of the court order.
They say that, to avoid a further hearing, they wrote to the Department for Environment, Food & Rural Affairs (Defra), asking for the draft plans and consultation to be supplemented, but had their request rejected.
ClientEarth CEO James Thornton said: "The draft plans for Scotland, Wales and Northern Ireland are simply plans for more plans.
"The court ordered a plan for the UK Government to obey the law on pollution limits across the UK as soon as possible.
"The health of all UK citizens is at stake, not just some."
Limits for nitrogen dioxide (NO2) were introduced by EU law in 1999, and were to be achieved by 2010.
Air pollution is linked to an estimated 40,000 early deaths a year in the UK, and some 37 out of 43 regions of the country are in breach of legal limits for nitrogen dioxide.
In May, the Government said that local authorities would now be expected to develop new and creative solutions to reduce emissions as quickly as possible, while avoiding undue impact on the motorist.
Consultation on a range of measures that could be taken ran until June 15 and the final plan is due to be published by July 31.