The Prison Officers' Association has said members of organised criminal gangs in prison are as difficult to deal with as dissident republican inmates.
The POA expressed concern that the Government is trying to take an allowance from prison officers for working in Ireland's maximum security prison in Portlaoise, where the most dangerous inmates are held.
The association said the removal of this allowance is unjust and unfair as Portlaoise is unique because it is patrolled by the army.
The association also said there has long been a difficulty with criminal gangs feuding in the country's prisons, taking control of aspects of the prisons and intimidating inmates who want to comply with the prison regime
At the POA's annual conference in Sligo, officers also raised the issue of overcrowding, saying it remains a serious problem, particularly in the Dochas Women's Prison, in Cork Prison and in Castlerea Prison.
The POA said it is also totally unacceptable that there are plans to double up inmates in cells in the new prisons that are being built.
Concerns over the actions of some violent prisoners were also expressed, with claims that some inmates are acting with impunity.
Prison officers said they do one of the most dangerous jobs in the country as they are subject to attacks from prisoners.
In the last week, two officers at Mountjoy Prison had boiling water thrown over them, another was beaten in the head and another officer had blood smeared on his face.
The POA said the Irish Prison Service is not being tough enough on violent inmates.