A second suspected suicide of an inmate at Maghaberry jail in two weeks has prompted a call for major Prison Service reform.
Life sentence prisoner Barry Cavan, from north Belfast, died in the high-security jail on Tuesday evening.
His death came in the same month that 44-year-old remand prisoner Gerard Mulligan, from Lisburn, killed himself.
There have been four suspected suicides in Maghaberry, near Lisburn, this year.
Ulster Unionist Assembly member Doug Beattie voiced concern that "under-investment" and management issues were contributing to a negative environment in the prison.
He cited a recent episode of industrial action by prison staff protesting over pay and conditions.
"How many more prisoners have to lose their lives before our Executive realises there is an issue in our prisons and with our Prison Service that will not go away until decisive and strategic action is taken," Mr Beattie said.
The acting director general of the Northern Ireland Prison Service (NIPS), Phil Wragg, described the death as an "absolute tragedy".
He said he was unable to provide an assurance that there would be no suicides in the future.
"No prison service anywhere in the world could give anybody that assurance," Mr Wragg told BBC Radio Ulster.
He said the service took its duty of care to prisoners "very seriously".
Mr Cavan, who was in his late 20s and from the New Lodge area, was sentenced to a minimum of 13 years after he admitted the 2012 murder of neighbour David Corr in a frenzied knife attack.
The NIPS said: "The next of kin have been informed and the Prison Service has expressed their sympathy to the family.
"The PSNI, coroner and prisoner ombudsman will conduct a full investigation into the death."