The Irish Penal Reform Trust has called for the abolition of solitary confinement in prisons.
It comes as the organisation's director says many prisoners are being asked to be placed in confinement due to a "fear of violence".
The report contains 25 recommendations focusing on the use of solitary confinement and restricted regimes in Ireland.
It has said holding prisoners in isolation for extended periods of time must be abolished due to the harm it can cause to prisoners' mental health.
The report calls for the abolition of solitary confinement, which requires prisoners to be alone for 22 hours a day.
It also wants the gradual elimination of the use of restricted regimes where prisoners are alone for 19 hours a day.
The organisation has said more than 379 prisoners requested to be on restricted regimes last year due to a fear of violence.
It said the Irish Prison Service needs to research and develop a range of initiatives to address violence in prisons.
Former UN special rapporteur on torture Juan Méndez will make a keynote address at the publication of the report later today.
Deirdre Malone, Director of the IPRT, said there has been an increase in the number of prisoners who are placed in solitary confinement compared to five years ago.
Speaking on RTÉ's Morning Ireland, she said in its latest research, it found that last year around 11% of the overall prison population were locked up for 19 hours or more a day.
She said what is particularly significant is that many prisoners are being asked to be placed in a restricted regime or solitary confinement because of "a fear of violence".
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"We would recognise the challenge for any prison service where they are faced with a prisoner who is making this request and they are tasked with balancing this prisoner's safety with trying to provide a reasonable and humane regime," she said.
Ms Malone said solitary confinement is 22 or 23-hour lock ups with no access during those lock-ups, while restricted regime is 19 or more hours a day locked up.
She said there are three main reasons why they are calling for solitary confinement to be abolished.
"The first is really that human rights principles require prisons to be safe and respectful," Ms Malone said.
"It's impossible to achieve those goals in a regime where prisoners are isolated for long hours.
"The second is that isolation reduces access to activities that promote rehabilitation.
"The third is that prolonged isolation can have devastating effects for mental health and that is everything from sleep deprivation and paranoia right through to rage and depression, and we see higher rates of suicide and self-harm."
She said what happens in prisons often reflects what is happening "on the outside".
"There were, of course, reports of fear of violence, threats of violence, gang warfare and drugs availability.
"What we would be asking for is both the Minister for Justice and the Irish Prison Service to consider the end point of creating so many prisons within prisons and to look at some of the solutions."
