More than 120 lawyers have vowed to not act against activists from groups such as Extinction Rebellion and Just Stop Oil who are "exercising their democratic right of peaceful protest".
They have published a "Declaration of Conscience", and face the prospect of disciplinary action.
The chair of the Bar Council Nick Vineall KC said it was "disappointing".
Barrister Paul Powlesland, who signed the declaration, said: "We're refusing to advise fossil fuel companies on how to dig for new oil and gas, the same way we wouldn't advise a killer how to commit serial murders."
The group, who call themselves 'Lawyers Are Responsible', say they will withhold their services supporting new fossil fuel projects and any action against climate protesters who are "exercising their democratic right of peaceful protest".
They have called upon the government and their colleagues to "act urgently to do whatever they can to address the causes and consequences of the climate and ecological crises and to advance a just transition to sustainability".
Climate groups like Just Stop Oil, Extinction Rebellion and Insulate Britain have made headlines in recent years through their tactics which include blocking motorways and gluing campaigners to buildings.
They now face the prospect of disciplinary action for breaching professional regulations such as the so-called 'cab rank rule', which requires lawyers to take on any case within their competence.
The declaration has been organised by climate group Plan B, which said some of the lawyers had self-reported to the Bar Standards Board.
In a statement, the charity said: "This is understood to be the first time in legal history that barristers have engaged in a collective act of civil disobedience."
This comes a few days after the scientific body that advises the UN on rising temperatures released a new report saying clean energy and technology could be exploited to avoid the growing climate disaster.
The group of legal professionals includes some prominent members such as the chair of the British Institute of Human Rights Sir Geoffrey Bindman KC.
Fellow signatory Michael Mansfield KC said: "I live on planet earth but I do not own it.
"I see myself as a custodian whose good fortune and responsibility is to represent its interests and those of fellow guardians."
Tim Crosland, the director of Plan B, called for an end to new fossil fuel developments.
He said "behind every new oil and gas deal sits a lawyer getting rich" while "ordinary people of this country" take a stand.
"The rule of law has been turned on its head. Lawyers are responsible. It's time to take a stand."
In a statement, Mr Vineall said: "The cab rank rule prevents barristers from refusing work because they disagree with the actions or views of those seeking their services."
The rule "promotes access to justice and promotes the rule of law", he said, adding: "It is disappointing that some lawyers apparently wish to remove these rights from people of whom they disapprove."
"I would be profoundly unhappy if a climate change activist accused of a public order offence were ever to be precluded from obtaining the services of the barrister of their choice because their chosen barrister happened to disapprove of the particular way in which they had been protesting," he said.
Plan B said the declaration would be launched on 29 March outside the Royal Courts of Justice.
MP and former solicitor general Robert Buckland said it was a "very odd approach" and "not really consistent with the role of a lawyer."
"When lawyers start picking and choosing, in a way it undermines the independence of the legal profession", he told the Daily Mail.
He added: "There are plenty of people lawyers represent who are deeply unpleasant and deeply unpopular, such as rapists and paedophiles.
"But they are entitled to a fair trial."