Little has been done to help vulnerable prisoners or tackle drug abuse at Northern Ireland's only high security jail, inspectors have found.
The review by the North's Criminal Justice Inspectorate (CJI) has raised significant concerns over support for inmates suffering mental health difficulties and the availability of illegal and prescription drugs at Maghaberry Prison.
Chief Inspector Brendan McGuigan said: "While the inspection team welcome the progress that has been made and the momentum to deliver change at Maghaberry which has built up since May 2015, I reiterate our view that significant risks remain, particularly around prisoner safety, which have the potential to drag the prison back to where it was 18 months ago."
The review comes in the wake of two suspected suicides at the Co Antrim facility over recent weeks.
Prison chiefs were also heavily criticised in a damning Ombudsman report after an inmate blinded himself during an extreme episode of self-harm in the prison two years ago.
Mr McGuigan said: "Inspectors found that while mental health support and assistance provided to new prisoners has improved since January 2016, there was still no overall safer joint custody strategy in place to comprehensively address safety issues, for those who were vulnerable.
"This is a serious omission which was impeding work in tackling vulnerability."
A death in custody action plan was not being monitored to ensure that adequate support was provided to those at risk to suicide or self-harm, it was also found.
Although Maghaberry's drug problem has been well documented, inspectors noted no significant progress in dealing with the issue.
Mr McGuigan added: "The high level of prescription drug availability and use by prisoners remains a significant concern, especially given the volume of divertible medication held by prisoners themselves, which can result in vulnerable prisoners being bullied by others to hand over their medication.
"There were also problems in accessing addiction services and no coordinated, recovery-based approach to addressing the significant substance misuse issues which exist within the prison population."
Last week medics from the South Eastern Health and Social Care Trust, which provides healthcare in prisons, cautioned that further episodes of extreme self harm could not be ruled out because up to 60 mind-altering substances were being abused.
Maghaberry houses almost 1,000 prisoners, including around 50 with loyalist and republican paramilitary affiliations who are held in separated accommodation.
Dissident republicans have issued death threats against prison staff in recent years and in 2012 long-serving officer David Black was shot dead by dissidents as he drove to work.
Last May, a joint assessment by HM Inspectorate of Prisons and the CJI said it was a prison in crisis; among the worst in the UK.
The most recent review was not designed to replicate the 2015 full inspection but aimed to assess progress on nine recommendations.
The inspection team, which comprised experienced officers from Criminal Justice Inspection Northern Ireland, Her Majesty's Inspectorate of Prisons in England and Wales, the Regulation and Quality Improvement Authority and the Education and Training Inspectorate, carried out their three-day review of Maghaberry in early September.
Among the more positive outcomes inspectors noted an appetite for change with managers now located within the houses for which they were responsible, resulting in a more hands-on management style.
They also said a more dynamic approach to security had been adopted with staff routinely supervising association areas within Maghaberry.
Mr McGuigan said: "At the time of the visit in September the prison was more settled and calm. Prisoners were experiencing a more predictable routine, focused around a core day where prisoners attended work, education or other activities and where fewer lockdowns and regime restrictions occurred.
"Maghaberry continues to be a complex prison operating in a difficult environment, so we must be realistic in terms how quickly the change required and work undertaken to modernise Maghaberry, can be achieved."