Complaints made to Northern Ireland's Prisoner Ombudsman by inmates inside the region's jails have increased by 10% in a year, the watchdog said.
Ombudsman Pauline McCabe said the 407 eligible allegations covered a wide range of issues, including lockdown regimes, access to activities and procedures around family visits.
The concerns are forwarded to Mrs McCabe if the prison service's internal complaints system fails to achieve a resolution.
The ombudsman, publishing her final annual report before stepping down from the role later this month, said while progress had been made to reform the region's prisons there was still much left to do. She said fundamentally there were still too many prisoners with not enough to do while serving their time.
There are around 1,800 prisoners held in the region's main prisons at Maghaberry, near Lisburn, Magilligan in Co Londonderry and Hydebank Wood young offenders and women's prison in south Belfast. Proportionally the most complaints came from prisoners inside Maghaberry - Northern Ireland's only high-security facility.
The ombudsman is tasked to investigate complaints and deaths or near death incidents in custody. There have been 42 deaths inside Northern Ireland's jails since 2005. While natural causes account for the majority, Mrs McCabe has had to examine a number of prisoner suicides during her five-year stint in office.
"Prison reform is now under way and there is widespread recognition of, and commitment to, the need for change," she said as the annual report was published at Parliament Buildings, Stormont.
"I am proud of the role that the office has played in developing awareness of the need for reform and my hope as I conclude my role as Prisoner Ombudsman is that the reform programme will continue to be implemented with zealous determination and dedication by everyone who has a role to play. There have certainly been a number of encouraging developments. In particular, the severance and recruitment programmes are well under way; new rationalised structures, staff profiles and shift patterns are being implemented; and a change team with responsibility for producing a forward plan is now doing its work.
"However, there is still much to be done and a number of factors are significantly impacting upon the quality of regime offered to prisoners. Crucially, there are far too many prisoners with not enough to do and the work required to deliver a programme of purposeful, rehabilitative activity for every prisoner must be taken forward with great urgency."
In the last year, Mrs McCabe published investigation reports into the deaths in custody of six prisoners and completed the first "near death" investigation following an attempted death by suicide at Maghaberry. There are currently eight ongoing death in custody investigations.