There were fewer prisoners at Prescoed prison in Monmouthshire last year, new figures show.
A penal reform charity warned prison overcrowding and a lack of resources contribute to a "failing system", and called on the Government to jail fewer people and reform the probation service.
The Ministry of Justice figures come after the Government re-enacted Operation Safeguard in March, requiring police stations to set aside cells for prisoners when jails are close to capacity, following an increase in the number of people detained across England and Wales.
It shows there were 231 prisoners at Prescoed prison in Monmouthshire at the end of March – down from 259 a year earlier.
Meanwhile, there were 87,919 prisoners in England and Wales at the end of March – in line with a year earlier, but up 3% from December 2024.
Although 15,730 people were released from prison between October and December last year, up 23% on the previous year, some 10,401 people were recalled to prison across the same period – up 45% on the previous year.
The Ministry of Justice said measures aimed at tackling prison overcrowding, including early releases, and the expansion of the Home Detention Curfew, likely contributed to the growing recalled population.
Andrew Neilson, director of campaigns at the Howard League for Penal Reform, said: "Prisons have been asked to do too much, with too little, for too long, and these prison population figures show that even the early release of thousands of people has not been able to solve this problem for good."
He said more than half of prisons in England and Wales are overcrowded, adding "the situation is unsustainable".
He warned: "Overcrowding and lack of resourcing are contributing to a failing system where the needs of people in prison are overlooked and unmet.
"It could not be clearer that further action is necessary.
"We must send fewer people to prison, curb the use of recall after release, and prioritise delivering an effective and responsive probation service that works to cut crime in the community."
Pia Sinha, chief executive of the Prison Reform Trust, said: "The prison population is once again approaching record highs, with the breathing space bought by emergency release measures fast disappearing.
"A key driver of this crisis is the rising number of people being recalled to custody, trapping individuals in the criminal justice system rather than supporting their rehabilitation."
She said "urgent action" is needed, adding this should start with the end of short, fixed-term recalls and post-sentence supervision for people given short sentences.
"Tackling overcrowding through meaningful reform will help build a safer, more effective justice system for everyone," she added.
A Ministry of Justice spokesperson said it 'would not hesitate' to recall offenders who break the rules or cannot be managed in the community.
"However, the number of recalled offenders in prison has doubled since 2018, contributing to the prisons crisis this government inherited," they added.
"That is why we have reformed the recall and re-release process while retaining important safeguards to keep the public safe."