An activist group hopes to sue the UK government over climate change, arguing that it is discriminating against the young by failing to cut emissions fast enough.
The campaigners - known collectively as Plan B - argue that if the UK postpones emissions cuts, the next generation will be left to pick up the bill.
It is seeking permission from a judge to launch formal legal action.
The government has promised to review its climate commitments.
A spokesperson said it was committed to tackling emissions.
But Plan B believes ministers may breach the law if they don't cut emissions deeper - in line with an international agreement made in Paris at the end of 2015 to restrict global temperature rise to as close to 1.5C as possible.
A hearing is set to be held on Wednesday at the High Court.
What is Plan B's case?
The UK is currently committed to cutting the greenhouse gas emissions that fuel climate change. The government has agreed to reduce emissions by 80% by 2050. Plan B says this target is too weak to comply with the global agreement made in Paris.
It will argue that the UK is:
- Failing to make a fair contribution to the global challenge of climate change
- Acting irrationally given the severity of the threat
- Acting in a discriminatory fashion towards the young
- Breaching people's fundamental human rights to family life and to property
What is Plan B?
Plan B is a tiny legal group funded by crowdsourcing. It says that Plan A - relying on governments to solve the climate challenge - is failing, so a Plan B, involving legal action, is needed.
It's making the legal approach with 11 citizens aged from 9-79. One of them owns a home in the British Virgin Islands which was damaged by Hurricane Irma. Hurricanes may get stronger as the ocean heats.
Plan B's founder Tim Crosland told BBC News: "The government has got to take this issue more seriously. We're worried that the Treasury is trying to put a block on measures to protect the climate."
Does it have a chance of success?
The UK has lost court cases recently for failing to meet EU air pollution limits. The Plan B case is much less clear-cut. But climate court cases are emerging round the world.
In Holland, a group called Urgenda won a case in which the judge ordered the Dutch government to raise the ambition of its climate targets. The Dutch government has appealed the ruling, and a decision is pending.
What does the UK government say?
A UK government spokesperson said it would be inappropriate to comment on an ongoing court case, but stated that the UK would seek advice on the UK's climate targets after a big international meeting to discuss the 1.5C ambition in the Paris agreement later in the year.
"We are a world leader on clean growth, and since 1990 have reduced carbon emissions by more than 40% - faster than any other G7 country," the spokesperson said.
Ministers have previously said they'll review their targets in the light of the 1.5C goal. Plan B complains that the government hasn't actually commissioned a review. It says ministers haven't set any terms of reference, and they haven't set a time frame for it.
Last week, the government was rebuked by its own climate advisers for failing to cut emissions in line with its current commitments, and for passing the buck to the next generation.
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