Locking up at Maghaberry prison
Claims that prisoners are being mistreated during searches of their cells need to be investigated, the Prisoner Ombudsman has said.
Pauline McCabe has written to Security Minister Paul Goggins after dozens of complaints were made against Maghaberry Prison's standby search team (SST).
It is understood 50 complaints have been made in the last two years, but no-one has been charged.
Ms McCabe said police investigations should be independently reviewed.
"Twenty-three of the Maghaberry cases have been referred to the PSNI in 2008/09, 18 of them since October 17 2008," said Ms McCabe's letter to the security minister.
"To date the Public Prosecution Service has considered eight of those cases and, in line with the above, made a decision of no prosecution in all cases.
"I believe that this is because the standard of evidence required to support a prosecution is not available where a case typically involves the word of one prisoner against three, four or even five officers."
The Ombudsman said further allegations of misconduct had been made privately by prison staff concerned at the conduct of colleagues, but she claimed none of these allegations had been officially lodged.
"I emphasise that I am not making any assumptions about the factual accuracy of information provided by prisoners in connection with particular allegations," she added.
Ms McCabe wrote: "It is, however, a matter of great frustration to me that prisoners are raising these matters, and asking for me to investigate and I am unable to do so because of the requirement for the internal complaints procedure to be exhausted."
But in a statement the Prison Service said it had already started a a review of the SST's role at Maghaberry in order to ensure that its work is carried out effectively.
It added: "The primary role of the Standby Search team is to search for contraband and illicit materials, particularly drugs.
"There have unfortunately been drug-related deaths in prison and were it not for the efforts and vigilance of the SST there would have been potential for further loss of life.
"Because of the role they perform it is not surprising that prisoners may make complaints against SST team members.
"All complaints of assault by a member of staff on a prisoner are immediately reported to the PSNI."