Report is critical of Northern prison service
More than a third of recommendations made after a Criminal Justice Inspection Northern Ireland (CJINI) report into the country's prisons have not been "met in full" over a year later.
That is the conclusion of a follow-up to the group's November 2010 report into mistaken prisoner releases.
Four more prisoners had been released by mistake since then, the group said.
It added it was disappointed at the overall pace of change.
CJINI acknowledged there had been significant effort by the Northern Ireland Prison Service (NIPS).
However, it said the work of the NIPS had "been focused on longer term process re-engineering and fundamentally neglected the immediacy of the ongoing risks".
CJINI said that of the 25 NIPS recommendations following its initial report, 14 (56%) can now be said "to be met in full".
It said a further 10 (40%) can be said to be partly completed and one (4%) discharged (no longer relevant).
Dr Michael Maguire, chief inspector of Criminal Justice Inspection said: "Well over one-third of the recommendations made have not been met in full some 15 months after the first report.
"For example, it is disappointing that formal training for front-line staff has still not been delivered, with the most notable for duty governors who are expected to authorise final release.
"There is also a need for job guidance and a continued focus on the full implementation of existing controls by way of supervision and quality checks.
"Compliance and quality assurance with robust mechanisms must be sustained.
"Both the operational and strategic focus needs to be maintained on the issues, and ultimately, the accelerated completion of all the outstanding recommendations."
Justice Minister David Ford has instructed the prison service to "fully implement" the outstanding recommendations within the next six months.
He said he agreed that "despite considerable progress, the pace of change needs to quicken".
"This report recognises the encouraging work and significant investment undertaken by the prison service to address this issue," he added.
"However, it also identifies the need for the completion of the outstanding recommendations and I have instructed the prison service that this work must be finished by the end of September."
Dr Maguire said the potential release in error of any prisoner could be a public protection issue.
"We need to strive for 100% accuracy where we can and that means getting the thing right at source, providing support to front-line training and making sure the right check and balances are in place is important," he said.
Mr Ford acknowledged that the prison service had been criticised for the erroneous release of prisoners, but said the efforts of staff and management since then to address the problem deserved recognition.
"I agree with Dr Maguire's statement that even when all the recommendations have been implemented in full, the risks of erroneous releases cannot be entirely eliminated," he said.
"The prison service discharges around 4,500 prisoners from custody each year and is currently operating at an accuracy level of 99.74%, comparable with other services.
"Despite this, there can be no room for complacency and improving its arrangements to safeguard against further erroneous releases is part of fundamental change programme being undertaken by the prison service."