The Law Society has warned that a “chronic” lack of new duty solicitors could lead to innocent people being found guilty.
A 20-year pay freeze has rendered the job unattractive and could see more people representing themselves in court, it added.
According to the BBC, nearly half of duty solicitors in England and Wales are aged 50 or over, reaching nearly two thirds in rural areas. Just 5% are under 35 in some parts of Wales.
The Ministry of Justice said it would ensure there were enough solicitors.
Richard Miller, 52, head of justice at the Law Society described the legal system as “creaking at the seams”.
The solicitor’s fee is currently different across each county.
Michael Strain, 52, who runs a law firm in Pwllheli, Gwynedd, said: “You are paid a flat rate. In Caernarfon police station it’s £172 a job.
“So I would be paid the same for up to three days at a police station on a rape case as I would for two hours where a teenager has smashed a window.”
Of the 6,104 duty solicitors in England and Wales only 11% are aged under 35.
The duty solicitor fee has seen no increase since 1998 and was cut by 8.75% in 2014 by the coalition government.
In that time, the average house price in Wales has more that trebled, rising from £48,294 to £162,374 – meaning the fee they earn is worth less than it was 20 years ago.
Mr Miller said: “We are coming close to a point where the criminal duty solicitor is becoming extinct in some areas…and if you have no solicitor, then there is no fair trial.
“Some people will have to go to court and represent themselves. They could be cross examining witnesses or even the victim themselves.
“Worst case scenario is that you could see innocent people found guilty, simply because they are up against an experienced prosecutor and there is no one to fight their corner.”
One solicitor, who wished to remain anonymous, claimed a number of people were already being questioned at police stations without representation – despite the right to free legal advice – as a result of the long wait for an available solicitor.
“That is happening now, and is going to happen more and more,” they added.
Mr Strain said his firm had been so short-staffed, his office has trained retired police officers to do the work.
“There is so little money in it now, that I couldn’t really hire someone on a full-time contract,” he said.
A Ministry of Justice spokesman said solicitors played a “vital role” in the criminal justice system and the department “routinely meets with legal professionals and will continue to engage with them to ensure a sustainable justice system”.
