Murder trials will collapse and paedophiles will walk free as a result of legal aid cuts, the man leading an unprecedented walk-out by barristers has warned.
Thousands of barristers have chosen not to attend proceedings at courts in cities including London, Manchester, Liverpool, Leeds, Birmingham, Newcastle, Winchester, Bristol and Cardiff.
The nationwide protest is the first in the history of the criminal bar.
The Government plans to cut fees as part of a bid to slash £220 million from the legal aid budget by 2018/19 - reducing them by as much as 30% in the longest and most complex cases.
Criminal Bar Association chair Nigel Lithman said the "strike" had the backing of almost every chambers and accused Justice Secretary Chris Grayling of "manipulating" official figures to falsely portray lawyers doing criminal aid work as high-earning "fat cats".
Mr Lithman told the BBC: "You are going to see cases collapsing, as they have already started. There are cases of murders, murder trials, that have collapsed because of them being inadequately prosecuted - that leads to enormous concerns for the victim's family.
"Secondly, the barristers will not work, they have made that quite clear, at rates that take them, as one person was telling me of his earnings today, at around £13,000 as a taxable income. That is a somebody with a law degree and a masters in public international law - why would they work at those rates?
"This is how the public will see it as far as prosecution is concerned - without people coming into the system there will simply be nobody of ability to prosecute serious cases.
"Where will paedophiles and rapists be living? Not doing the 100 year terms of which the Government speaks but, I am afraid, next door to the public."
The Ministry of Justice said it was vital to scale back the most expensive legal aid scheme in the world and insisted it will remain "very generous" even after the changes.
The department highlighted figures showing that 1,200 barristers judged to be working full-time on taxpayer-funded criminal work received £100,000 each in fee income last year. Six barristers picked up more than £500,000 each, it said.
But Mr Lithman, whose own case was moved to the afternoon, said the same official statistics showed that - after allowing for VAT and other expenses - the average barrister involved in the work earned around £36,000.
The Bar Council calculated that it was lower still - around the £27,000 national average, he said, meaning the cuts would push people away from the vital work.
"There are simply going to be no people of any ability prepared to do criminal legal aid work," Mr Lithman said.
In a dig at the release of the earnings figures, he said he had been contacted by one barrister who was earning £13,680 in her second year of practice.
"You can put out the earnings of five to 10 people, but you can't run the justice system on the efforts of five to 10 people," he said.
The Bar Standards Board has warned that any barristers who stay away from court will almost certainly be in breach of their professional code of conduct with "very serious consequences".
It urged the CBA to call off the action which it said could harm the interests of clients, others involved in a case and public confidence in the administration of justice.
The reforms also include limits on prisoners' access to legal aid, a household disposable income threshold for criminal legal aid and reductions in the cost of fees for representation.
Two brothers who allegedly plotted to travel abroad for terrorist training appeared in the Old Bailey without the assistance of their solicitors.
Jurors in the case of Muhammed Saeed Ahmed and Muhammed Naeem Ahmed were reminded by Old Bailey judge Gerald Gordon that the "lonely" courtroom was a result of the strikes taking place.
It was one of a number of cases to suffer setbacks as a result of today's action.
Around 70 barristers gathered outside Birmingham Crown Court to back the walk-out and hear Mark Wall QC read out a statement condemning the Government's proposals.
And around 150 protesters gathered outside the entrance to London's Southwark Crown Court where some pre-trial hearings were being held without all barristers present.
Many outside were dressed in their wigs and robes with some holding placards with the words "Save British Justice" and "No legal aid cuts".
Bristol Crown Court dealt only with cases involving vulnerable children and adults this morning, due to the walk-out.
Shadow justice secretary Sadiq Khan said: "No-one wants to see disruption in our courts but this unprecedented action shows how relations between the legal profession and David Cameron's Government have collapsed as a result of policies which could restrict access to our courts to only those who can afford it.
"The Lord Chancellor swears an oath to uphold the law of the land, so for Chris Grayling to have lost the confidence of the legal community he relies on to deliver on this oath is extremely worrying."
Frances Cook, chief executive of the Howard League for Penal Reform, addressed a protest outside Westminster Magistrates' Court.
After speaking, she said: "Abolition of legal aid for prisoners, including teenagers and mothers separated from their babies, is politically motivated and not based on hard financial sense.
"It will mean people spend months, or even years, longer in jail unnecessarily because will no longer get legal support to get the courses they need in prison and to move through the prison maze."
An MoJ spokeswoman said: "We entirely agree lawyers should be paid fairly for their work, and believe our proposals do just that.
"We also agree legal aid is a vital part of our justice system - that's why we have to find efficiencies to ensure it remains sustainable and available to those most in need of a lawyer.
"Agencies involved in the criminal justice system will take steps to minimise any upset court disruption could cause for victims and witnesses involved in trials."