David Bennett, from Wallich, Wales’s largest homelessness charity, claimed most drug-related deaths “are preventable if we treat drug use as a health, not criminal justice, issue”.
“Housing, health and justice need a joined-up approach,” he said.
He said the charity supported “conversations to devolve justice and policing” and said without “co-ordinated” support prison leavers were “being set up to fail”.
“The war on drugs hasn’t worked,” he added.
The report also says homelessness among former prisoners in Wales is continuing to rise.
The number of people leaving prison, supervised by Welsh probation services, who were recorded as rough sleeping on the day of their release rose by 24% in 2025-26.
In total, 695 prison leavers managed by Welsh probation services were rough sleeping on the day of their release.
Other findings include that more than a third (39%) of all custodial sentences given to women in Wales in 2025 were for offences related to thefts from shops.
Meanwhile, people from black ethnic groups in Wales remained the most overrepresented ethnic group in the prison population in 2025.
There were 58 black people from Wales in prison for every 10,000 of the population, compared with 15 white people per 10,000 of the population.
A spokesperson for the Welsh government said: “Every drug-related death is a tragedy.
“We are working closely with health boards, local authorities, Public Health Wales and other key partners to reduce the harms caused by substance misuse, focusing on early intervention, prevention, treatment and recovery support.”
They added that the findings “strengthen the case for the full devolution of justice to Wales”.
“Bringing responsibility for justice into line” with devolved services “would enable a more effective and joined-up approach to improving outcomes, reducing reoffending and building safer communities across Wales”, the spokesperson added.
A Ministry of Justice spokesperson said: “We inherited prisons in crisis but we’re acting on all fronts, including by reducing the number of women in custody through investment in community services and cutting the flow of drugs into prisons.
“In Wales we invest more than £3.4m into services which work across prisons, probation and courts to help support prison leavers overcome their addiction.”
They added that prisoners at risk of becoming homeless can be offered temporary accommodation by the prison and probation service.
Chair of the Welsh Affairs Committee at Westminster, Ruth Jones, said: “It is devastating to hear that more than a third of all deaths among prison leavers in Wales were due to drug poisoning, and that the number of homeless prison leavers in Wales has increased.
“The data underscores the findings of our inquiry that reported earlier this year: the prison and probation system is struggling with increasingly complex demand, which has serious implications for rehabilitation outcomes.”
She added: “Improving Wales-specific justice data is something my committee has consistently pressed the UK government on, and in light of several of Dr Jones’ data requests to the Ministry of Justice not receiving a response, it is clear that there is still work to be done here.”
Additional reporting by David Deans.