Justice Minister Dermot Ahern has dismissed suggestions that overcrowding was to blame for a riot at Mountjoy jail in which three officers and an inmate were injured.
More than 70 prisoners barricaded themselves into an exercise yard in the Dublin prison and armed themselves with makeshift weapons for two and a half hours on Thursday night.
The riot broke out after an inmate was refused access to the yard and an officer was attacked. Two other officers were then injured when prisoners assaulted them with pool cues and balls in the jail's A-wing.
Mr Ahern defended his record and said extra prison spaces were being built around the country.
He said 176 cells were being opened in Wheatfield, along with a new block in the high-security Portlaoise jail, while 70 additional places will be available in the Dochas, the state's women's prison, by the end of the year.
"There is a problem in relation to the numbers of people in our prisons. But unfortunately we cannot put up a 'no vacancy' sign," Mr Ahern said.
The Irish Penal Reform Trust (IPRT) claimed conditions at the Dublin jail were hindering the work of officers, but Mr Ahern said overcrowding had nothing to do with the disturbance.
"I would suggest to people who rush out on to the airwaves, well-meaning as they may be, that they should not be blaming this particular incident on overcrowding in Mountjoy when it was not patently the case in this instance," the minister said.
The country's prison population reached more than 4,400 during the week, according to the Irish Prison Service (IPS).
Mountjoy has repeatedly held more than 700 inmates since May despite the Inspector of Prisons stating in February last year that the population should not exceed 600.