More than a third of deaths of former prisoners on probation in Wales in a year were drug related, according to a new report.

The Wales Governance Centre at Cardiff University published the report and urged politicians to tackle "systematic failures" in the criminal justice system.

Report author Dr Robert Jones called on the UK and Welsh governments to find a solution to the "tragic" situation.

The Welsh government said it was working to reduce "harms caused by substance misuse", while the UK government said it was spending £3.4m to support prison leavers to overcome addiction.

According to the report, 37% of all deaths among prison leavers supervised by probation in Wales in 2024-25 were drug related.

The number of drug poisonings where the intent was "undetermined" in Wales accounted for 19 of the 52 who died.

Jones said this was "substantially higher" than the proportion across England and Wales as a whole, where deaths in this same category accounted for just over a fifth (21%) of the total - 131 out of 620.

Criminal justice in Wales is controlled by Westminster.

The Plaid Cymru Welsh government, and the previous Labour administration in Cardiff before it, argue it should be devolved.

Speaking to BBC Wales, Jones said the research looked at UK government data including Freedom of Information requests.

He said: "The added shock value to this is that these data point towards some systematic failures with incredibly tragic circumstances and consequences.

"Yet there isn't really a particular debate or discussion ongoing at the moment about these deaths, and indeed their causes, and how we might actually find a solution to them."

Jones said many areas of social policy, including "responsibility for tackling substance use, housing, education and local government" were devolved to the Welsh government.

"So what tends to happen is that criminal justice matters can often fall between the gaps between debates in the Senedd and debates in Westminster," he added.

Jones said the report raised "important questions about the current devolution settlement and whether the Welsh government has the powers and levers necessary to address the underlying causes of many of the challenges facing Wales".

He added: "Only by confronting the realities highlighted throughout this report can politicians and policymakers hope to overcome the many challenges facing communities across Wales."

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.

That suggestion was dismissed by Reform Senedd member Adrian Mason.

"The idea that the answer to drug deaths is more devolution is demonstrably wrong, as proven by Scotland," he said.

"In Scotland, justice is devolved and run by nationalists, and they have the highest drug death rates in the whole of Europe.

"The people of Wales expect politicians to get on with the day job rather than pushing for more and more powers at every turn."

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.