Criminal courts across England and Wales will be severely disrupted on Monday morning when barristers and solicitors stage an unprecedented mass walkout in protest at government plans to slash legal aid fees by up to 30%.

It is the first time barristers have withdrawn their labour, according to the Criminal Bar Association, and the first time the two wings of the legal profession have taken co-ordinated, national action.

Thousands of barristers and solicitors working on publicly funded cases are refusing to enter court for a half-day demonstration aimed at forcing the justice secretary, Chris Grayling, into a last-minute rethink of proposals designed to save £220m a year.

Lawyers have been careful to avoid describing the action as a strike because that would raise questions about contractual obligations to the Legal Aid Agency. But criminal barristers say the protest reflects mounting resentment over successive reductions in legal aid fees, which have already resulted in cuts of 40% for criminal cases since 1997.

They warn that if the Ministry of Justice enforces the latest reduction it will lead to lower quality legal representation, miscarriages of justices and more criminals walking free from court. No other public sector has been subjected to such swingeing cuts, they argue.

The protest has been co-ordinated with the Justice Alliance, which is supported by trade unions, charities and organisations such as Amnesty UK, Liberty, Unite, the Howard League for Penal Reform and the Children's Society.

Among those addressing a demonstration outside Westminster magistrates court in London will be Janis Sharp, the mother of computer hacker Gary McKinnon who fought extradition to the US. She said: "Without legal aid, unless you have money, you'll have no access to justice.

"For all the future Garys who find themselves needing astute legal advice, I plead with the government and politicians from all parties to think again before implementing cuts that would affect our most vulnerable. Cuts which would take a moment to impose but whose damage would take a lifetime to reverse."

Over the past year, senior judges have also signalled their concern about the scale of legal aid cuts. The courts service, however, views Monday as a "normal working day". The lord chief justice, Lord Thomas, warned judges before Christmas of the planned disruption. His note stressed that the judiciary was "constitutionally independent" and that "Monday 6th is a working day and as such, the business of the court will go ahead as normal".

In some cases, applications have been made to adjourn. "All decisions on the [day] itself are for the judge listed to hear the case," the note concluded. Judges and magistrates could summon lawyers to account subsequently for unscheduled absence but judicial retribution is not expected.

Chris Grayling, the justice secretary. Photograph: Sean Dempsey/PA

Some cases will not be affected. Nigel Lithman QC, the CBA chairman, said those involving vulnerable individuals, such as rape victims, would not be disrupted. The Law Society, which represents solicitors , will ensure that duty solicitors are available for suspects who were held in police custody over the weekend.

The legal aid dispute has become more polarised as the MoJ attempts to portray criminal lawyers as overpaid fat cats, and criminal barristers retaliate by pointing out that figures based on gross fees are wildly misleading.

Figures released by the MoJ show that 1,200 barristers earned a minimum of £100,000 each from criminal legal aid last year. Barristers contend that by the time VAT, chambers fees, pension provision, travelling and other expenses have been deducted, that figure is equivalent to a minimum of £50,000 each in taxable income. The CBA says the figures are further skewed by including fees often received for work carried out over several preceding years.

"Why not publish the incomes of top surgeons?" Lithman asked. "Why not show the politicians who have incomes from property? We are being singled out. Why such contempt for the criminal bar?"

The MoJ figures show that criminal barristers had a median fee income of £56,000, Lithman said, but that was before all other costs had been deducted. "Some barristers are earning as little as £13,000 a year. We are seeing more and more bankruptcies in the junior bar. Many are earning less than £25,000 a year."

Lithman said experienced barristers were deserting the criminal justice system. "It will lead to a collapse in standards of representation, more miscarriages of justice and more of the guilty going free."

He said legal aid costs had already fallen rapidly, resulting in a £60m underspend last year.

Steve Hynes, director of the Legal Action Group, said the MoJ figures showed the number of barristers earning more than £250,000 from legal aid had more than halved between 2009 and last year.

Matt Foot, a solicitor and founder of Justice Alliance, said: "There is widespread opposition to Grayling's proposals. They will have a devastating effect on the rights of ordinary people in this country and undermine the ability to challenge unlawful government actions."

No one has stood up and supported these proposals."

Nicola Hill, president of the London Criminal Courts Solicitors Association (LCCSA), said: "Monday will be a demonstration of how courts will look if these devastating proposals are implemented. It will be a glimpse into the future for both the government and the public where there'll be a pitiful lack of criminal defence solicitors who can offer rigorous, high-standard representation. As Gary McKinnon's case illustrates, justice needs to be available to all, not just the wealthy."

Andrew Langdon QC, the barristers' leader of the western circuit, said: "If these cuts go through, we will have a two-tier system. Defendants on legal aid are going to get less qualified lawyers who have less time to devote to their case. There will also be an increase in guilty people getting away with it.

"No other public service has suffered cuts of this order. We are self-employed people. There's never been any action like this before. A lot of individual barristers are worried about [their clients] but that fact that this is happening tells you a lot about the strength of feeling. We have a sense of responsibility that this is happening on our watch. We have to bring it to the public's attention."

Max Hill QC, a former chairman of the CBA, said the earliest record of barristers was at Lincoln's Inn in 1466. "This is the first and only time such action has been taken," he said.

Des Hudson, chief executive of the Law Society, said: "We understand why some people feel the need to take this action and respect people's right to do so." The Law Society is paying for criminal law training courses during the morning for those solicitors not attending court."

An MoJ spokesperson said: "At around £2bn a year we have one of the most expensive legal aid systems in the world, and it would remain very generous even after reform."Latest figures show more than 1,200 barristers judged to be working full-time on taxpayer-funded criminal work received £100,000 each in fee income last year, with six barristers receiving more than £500,000 each.

"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."