A lawyer and three politicians have dropped their legal challenge in Ireland on whether Brexit is permanent.
Papers were lodged in the High Court in Dublin earlier this year in a bid to seek a ruling on the issue from the European Court of Justice.
But Jolyon Maugham QC, director of the Good Law Project, said the length of time the challenge will take and the costs involved have forced them to ditch it.
Some £70,000 raised through crowd-funding for the case will be spent on legal fees already incurred with whatever is left over going to other Brexit challenges or charity, he said.
"Along with the other plaintiffs, Jonathan Bartley, Keith Taylor and Steven Agnew, I have taken stock of progress made on the Dublin case, its prospects going forward and changes in the wider political setting," he said.
"With regret, we have agreed between us and with Ireland that the litigation should be discontinued."
Mr Bartley is co-leader of the Green Party of England and Wales, Mr Agnew is outgoing Stormont Green MLA and Mr Taylor is a Green MEP for South-East England.
They had hoped the case would establish that the Article 50 notification to start Brexit negotiations, which Prime Minister Theresa May triggered in March, can be revoked.
Mr Maugham said their decision to drop the legal challenge did not mean Brexit is inevitable.
"Each of the (European) Council, (European) Commission and European Parliament has said the United Kingdom could withdraw the Article 50 notice with agreement," he said.
"There is no doubt this is so."