A record proportion of trials were postponed at Cardiff crown court during a period which saw barristers go on strike across England and Wales, new figures show.
The Law Society said the impact of years of budget cuts is "plain to see" in the latest figures, which also reveal the backlog of crown court cases reached a new high across the country last summer.
Ministry of Justice figures show that of the 157 trials listed at Cardiff crown court between July and September 2022, 88 (56%) were 'ineffective', meaning they had to be postponed to a later date.
This was the highest proportion for July to September any year since records began in 2014 – in the three months to September 2014, just 10% were ineffective.
Trials can be labelled as ineffective for a range of reasons, including the defence or prosecution not being ready, or witnesses being absent.
Meanwhile, 17% of trials at Cardiff crown court were 'cracked' last year – when the Crown Prosecution Service drops the case or the defendant pleads guilty – and 27% were effective, meaning the trial went ahead as planned.
Across England and Wales, ineffective crown court trials rose to their highest rate on record between July and September – 56% had to be postponed, up from 31% the previous quarter. A further 18% were cracked, and just 25% of trials went ahead on their scheduled date over the period.
Criminal barristers in England and Wales began an indefinite strike on September 5 2022 after their action against the Government's proposals for legal fees intensified
The walkouts ended in October, when members of the Criminal Bar Association accepted a package of measures, including a 15% legal aid fee increase for most crown court cases.
The MoJ said a lack of defence barrister availability due to the strikes was the main driver behind the high level of ineffective trials in the latest quarter.
Different figures show that the number of outstanding crown court cases across England and Wales also grew to a record 62,770 at the end of September – including 1,191 at Cardiff crown court.
Lubna Shuja, president of the Law Society of England and Wales, said: "The impact of decades of underinvestment in our criminal justice system is plain to see.
"The latest figures show huge backlogs in our criminal courts and unacceptably long delays for victims and defendants to access justice."
She added that criminal defence solicitors are "leaving in their droves" after more than two decades without a significant increase in legal aid rates.
“Unless the Government is willing to take the problem seriously, we will no longer have a criminal justice system worthy of the name," she said.
The MoJ said its latest figures indicate there was a slight reduction in the number of outstanding crown court cases between October and November.
A spokesperson said: "Whilst there was an increase in the crown court backlog during the barrister strikes, we have worked hard to reduce the caseload since.
"We are doing all we can to ensure courts are working at full capacity. Measures such as unlimited sitting days and increasing magistrates’ sentencing powers are helping restore the swift access to justice that victims deserve."