CRIMINAL courts across England and Wales will be "effectively inoperable" this morning, the man leading a walk-out by barristers over legal aid cuts predicted.

Criminal Bar Association chair Nigel Lithman said the "strike" had the backing of almost every chambers and said he expected "solid support" for the unprecedented action.

He accused Justice Secretary Chris Grayling of "manipulating" official figures to falsely portray lawyers doing criminal aid work as high-earning "fat cats".

The Government plans to cut fees as part of a bid to slash £220 million from the legal aid budget by 2018/19 - slashing them by as much as 30% in the longest and most complex cases.

The Ministry of Justice says it is vital to scale back the most expensive such scheme in the world and insists it will remain "very generous" even after the changes.

It criticised the action and highlighted figures showing 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 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," he said.

Protests are planned outside court buildings but Mr Lithman said those taking part in the action had made efforts to ensure there was "as little disruption as is proportionate" to cases.

His own case has been switched by the judge to the afternoon.

"Every head of chambers in the country said their barristers supported this and wanted to take part," he said.

"Courts in England and Wales will be effectively inoperable in the morning because of the size of this protest. There is solid support."

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 protest on Monday is the first in the history of the criminal bar.

"That it is necessary in order to try and prevent the slide of the criminal justice system into chaos and the criminal bar into oblivion makes it a sad day."

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.

But Mr Lithman said it would be "invidious" if any lawyers were punished given the widespread strength of feeling and the efforts made to minimise disruption.

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.

Former director of public prosecutions Lord Macd onald joined the condemnation of the cuts and accused Mr Grayling of "destroying something he doesn't really understand".

The Liberal Democrat peer said two MoJ ministers - Lib Dem Simon Hughes and Tory Lord Faulks - had expressed concerns and should have a "serious conversation" with Mr Garyling.

"These are people who are working extremely hard for low incomes and 30% cuts on top of that, in circumstances where the legal aid budget was underspent by £56 million last year, seems unreasonable," he said.

"I fear that Mr Grayling is in danger of destroying something that he doesn't fully understand which is a criminal justice system which is as good as any in the world, which is fair and which supports people who don't have money as well as people who do."

The protest was a "pretty dramatic" signal of the scale of concern, he suggested.

"These are not left-wing rebels, these are not natural rebels, these are people with families, with mortgages who have never done this before. I think it is a fair assumption they have been driven to it.

"I think the Government may not yet have fully understood the degree of concern, anger and indeed fear at the criminal bar and I hope that Lord Faulks and Simon Hughes will try and bring that home."

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."

An MoJ spokesman 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."