The Prime Minister's brother, Alexander Cameron QC, has succeeded in having a multi-million pound fraud trial thrown out on the grounds that the Government's legal aid cuts prevented his clients from securing barristers to represent them.
Mr Cameron, who agreed to represent the five defendants free of charge in the application to stop the case, argued that the controversial Ministry of Justice (MoJ) reforms meant his legally-aided clients could not find barristers of "sufficient competence".
The trial, which involves the alleged mis-selling of land to members of the public, is a so-called Very High Cost Case (VHCC). The Government has cut fees for such long and complex cases by 30% for barristers and solicitors.
In a landmark and damning decision, Judge Anthony Leonard QC stayed the proceedings at Southwark Crown Court, adding it would be a "violation" to allow the state more time to put right its "failure to provide the necessary resources to permit a fair trial".
Labour leader Ed Miliband said the Government's changes were "impeding access to justice", while solicitors working on the case warned the cuts were "endangering" the criminal justice system.
Delivering his ruling, Judge Leonard said adjourning the case to next January, as requested by the prosecution, would clog up the courts.
And he said he had no reason to think the defendants would be able to find suitably qualified barristers to represent them if the case was adjourned given the long-running dispute over legal aid cuts.
The judge said he had concerns there was "no realistic prospect that in the future a suitable advocate will be available" to take up the case.
He added: "Having considered all these matters, I am compelled to conclude that, to allow the state an adjournment to put right its failure to provide the necessary resources to permit a fair trial to take place now amounts to a violation of the process of this court.
"The knock-on effect on other trials, the waste of court resources and the need to disregard the Criminal Procedure Rules designed to protect the court system from abuse and to ensure that scarce resources are used to the best effect, all, in my judgement, add to the reason why an adjournment should not be granted.
"Even if I am wrong about that, I further find that there is no realistic prospect the sufficient advocates would be available for this case to be tried in January 2015 from any of the sources available."
Earlier this week, Mr Cameron, who declined to comment as he left the courtroom, had argued the case cut to a wider problem that there was only a finite pool of Queen's counsel barristers and very high demand for their services.
According to the Criminal Bar Association (CBA), each advocate who had signed a contract to undertake a VHCC case was presented by the Government with a choice either to accept a 30% cut in their fees or to terminate their contract. They chose to terminate their contracts.
Since then, the CBA understands that no barrister has signed a new contract to undertake a VHCC at the reduced rates.
The decision to stay the case means that the five men accused of being involved in a land banking scam will be free men - subject to any appeal by prosecutors.
Scott Crawley, Brendan Daley, Daniel Forsyth, Dale Walker and Arron Petrou were all charged with conspiracy to defraud and sat in the public gallery to hear the ruling. Forsyth was also charged with providing false information.
A further trial involving three other defendants which is linked to the case is still scheduled to take place.
But legal experts said it was "likely" they would launch an application to stay their case in light of today's decision.
Lee Adams, who represents defendant Forsyth, warned that controversial legal aid cuts were "endangering the criminal justice system".
And Mr Adams, a partner at Hughmans solicitors, praised the judge's ruling, saying it averted a potential miscarriage of justice.
Speaking outside court he said: "This is an unprecedented decision, it is enormous.
"This is absolutely the right decision because it is preventing a situation where innocent men may have been convicted for lack of proper representation.
"I think justice secretary Chris Grayling needs to think about his position very carefully, otherwise he risks the effective collapse of the most serious cases.
The MoJ said the UK has one of the most expensive legal systems in the world, which even after reform will still cost around £1.5 billion a year.
An MoJ spokeswoman said: "Barristers have refused to work on this case - and a number of other Very High Cost Court Cases - because they do not agree with savings the Government is making to legal aid.
"Even after the savings, if a QC picked up a case like this one, they could expect to receive around £100,000 for working on it, with a junior barrister receiving around £60,000.
"The Government has made sure that the Public Defender Service has a number of suitably qualified advocates who could act in this case."
The Prime Minister's official spokesman declined to comment on the case at a regular Westminster media briefing.
Labour leader Ed Miliband said: "We set out plans which could have avoided these changes.
"I believe they are impeding access to justice, I think they are a massive problem.
"I don't think they should go ahead in the form they are at the moment because it will frankly deny lots of people access to justice."
Shadow justice secretary Sadiq Khan said judges had lost confidence in Mr Grayling.
"This is an astonishing indictment of David Cameron's policies," said Mr Khan. "Time and again, ministers have been warned their changes to legal aid could lead to miscarriages of justice and trials collapsing.
Today, these warnings have come true.
"Because of Chris Grayling's legal aid changes, a judge has been forced to abandon a serious fraud trial because he couldn't guarantee the defendants a fair trial. Thousands of pounds of taxpayers' money have been wasted on this aborted trial, and this decision shows judges also have lost confidence in the Justice Secretary.
"Chris Grayling needs to urgently provide answers on how they plan to prevent a meltdown in the justice system caused by their policies."
Nicola Hill, president of the London Criminal Courts Solicitors Association, said: "Chaos reigns in the criminal courts at the moment.
"Barristers are refusing to work on complex trials. Solicitors not taking on new cases in Crown Court.
Expert witnesses are being paid so little they're refusing to prepare vital medical reports which some cases depend on.
"The foundations of justice in this country are starting to look very shaky. We're particularly concerned about the increasing number of defendants who are appearing in court without representation at all because they can't get a solicitor.
"They face serious criminal charges without being able to defend themselves properly. Courts are disrupted and the taxpayer ends up paying the extra costs of delays."
Asked if he was embarrassed about the case, the Prime Minister said: "We have an independent judicial system in this country and that's an important part of having a free country.
"My brother has made arguments on behalf of his clients in court and the judge has made a decision.
"That's the process, that's the way it should be."