Barristers are striking across England and Wales in a dispute over pay and conditions.
More than 1,000 cases will be impacted on each day of the strikes, the Criminal Bar Association (CBA) said.
Justice Secretary Dominic Raab said strikes would "only delay justice for victims" with courts already facing a backlog of 58,271 cases.
Kirsty Brimelow QC, deputy chair of the CBA, said the proposed 15% pay rise would not happen until the end of 2023.
By then, she told BBC's Today programme earlier, it would be too late to help and would not do enough to stem the flow of junior barristers leaving the bar.
Mr Raab urged barristers "to agree the proposed 15% pay rise which would see a typical barrister earn around £7,000 more a year".
But Ms Brimelow, speaking from the picket line outside Manchester Crown Court on Monday, told BBC Breakfast that the system had run on "good will" for a long time, including throughout the pandemic, with junior barristers working "ridiculous hours."
She said the issue had been "caused by government, not by barristers."
The criminal justice system is not functioning, Kirsty Brimelow said
As of the end of April, there was a backlog of 58,271 cases, according to HM Courts and Tribunal Service.
There were 567 criminal trials, including 60 sexual offence cases, that were unable to go ahead last year as there were no barristers to prosecute and defend them, according to Ms Brimelow.
The number of lawyers working in criminal justice - both barristers who appear before judges in court and solicitors who instruct them - has declined over the last decade, as many say they cannot make a living from the rates paid to them when they take on cases funded by legal aid.
Barristers have been warned that they could face disciplinary proceedings for misconduct if they don't turn up to court by the most senior judge in England and Wales, The Lord Chief Justice Lord Burnett.
But Ms Brimelow said the justice system was not functioning and there "has to be pressure for long-term gain."
Junior barristers are working for a "pittance" - and sometimes for nothing at all if cases are adjourned, barrister and author Chris Daw told BBC News.
He said that the 15% pay rise proposed by the government would not "touch the sides" and will be "wiped out by inflation" by the time it comes into effect.
If nothing changes, he said strike action could go on until August "or beyond".
Two young lawyers share their concerns about the profession
A shortage of barristers is causing "increasing misery to victims and those accused", as they are sometimes left waiting for years CBA chairman Jo Sidhu QC said.
He said barristers had suffered an average fall of 28% in their real earnings since 2006 and juniors in their first three years of practice earned a median income of just £12,200, which is below the minimum wage.
Mr Sidhu said almost 40% of junior criminal barristers left the profession in one year and that more than a quarter of specialist criminal barristers - around 300 - quit in the last five years.
He said: "In reality, our judges have been forced to adjourn 567 trials last year at the last minute because there simply wasn't a prosecuting or defence barrister available."
The strikes are intended to span four weeks, starting with walkouts on Monday and Tuesday and increasing by one day each week until a five-day strike from Monday 18 July to Friday 22 July.
Barristers are rallying at a number of high-profile courts that manage the most important cases in the country on Monday - including the Old Bailey, Birmingham, Manchester and Bristol Crown Courts.
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