Sex offenders and violent criminals are being freed from the UK's only remaining military jail "without any safeguards or probation supervision", inspectors have warned.
"Considerable gaps" in protection arrangements meant checks were not being carried out to establish whether some offenders could still pose a risk to the public after release from the Ministry of Defence's (MoD) Military Corrective Training Centre (MCTC) in Colchester, they said.
A prisons inspectorate report also found victims in the armed forces were not being told when detainees were returning to work alongside them.
Formerly a prisoner of war camp, the centre in Colchester is the last remaining of its kind and provides "corrective training" for service personnel detained under armed forces laws for anything from two weeks up to two years.
More than 260 people can be held at the site, but this has rarely exceeded 50 in recent years and stood at 33 at the time of the inspection in January.
There had been "some improvements in public protection since the last inspection, but considerable gaps remained", according to the report.
Although registered sex offenders were now subject to national monitoring under the so-called Multi-Agency Public Protection Arrangements (Mappa), "other sexual and violent offenders who fell outside Mappa's remit were released without any safeguards or probation supervision", it added.
"For detainees who had committed a sexual or violent offence, there was no systematic assessment of their risk of harm to others, or routine monitoring of their telephone calls or mail, either on arrival or when intelligence dictated, which undermined public protection measures.
"Child contact restrictions were not considered in all cases where potential risk existed.
"Victims working in the armed forces were not notified routinely of detainees returning to work alongside them."
Charlie Taylor, the chief inspector of prisons, said there was "no supervision for those convicted of a domestic violence offence who could return to their families".
The centre had "improved the oversight of detainees who were discharged into the community after a court martial conviction for a more serious sexual offence" but inspectors "continued to be concerned that some detainees, who had been convicted of violent offences and who could continue to pose a risk to the public, were not given any community supervision as the Armed Forces Act 2006 did not allow for it", he said.
Mr Taylor warned of an "anomaly" in regulations which meant detainees' phone calls or letters could only be monitored with permission from the defence secretary, recommending this power should be handed to the centre's commander who is "better placed to assess the risk that detainees may pose and understand where it is reasonable and proportionate to gather intelligence".
Overall, the centre was praised for its high standards and "strong rehabilitative culture".
The MoD has been contacted for comment.