Staff should have monitored Colin Bell because of his history of self-harming
An inquiry into the suicide of a NI prisoner has recommended the governor and deputy governor be subjected to a disciplinary investigation.
Colin Bell, 34, who was serving a life sentence at HMP Maghaberry for murder, hanged himself at the fourth attempt.
He was on suicide watch and was meant to be monitored every 15 minutes.
Northern Ireland Prison Service director Robin Masefield said that the standard of care was "unacceptable" and apologised to Mr Bell's family.
"There were unacceptable failings on that night and indeed in the previous days immediately leading up to Colin's sad death," he said.
He said that they were taking "robust action" and had already implemented one third of the Prisoner Ombudsman's 44 recommendations in a report on Mr Bell's death.
Mr Masefield said he had "confidence in the job being done at the moment in taking Maghaberry forward" by the governor and deputy governor at the jail.
He said there were 800 prisoners at the jail and many exhibited "challenging behaviour" and that overnight there had been 24 inmates considered to be at risk and kept under observation.
The Prison Governors Association also said they had confidence in, and supported, the governor and deputy governor at Maghaberry.
The 182-page report by Prisoner Ombudsman Pauline McCabe was published on Friday.
In October, 17 prison staff were suspended from duty following an internal investigation.
Not all of those suspended were on duty when Bell died.
One member of staff has since resigned.
It is understood that video camera footage examined as part of the investigation shows prison staff lying in bed watching television while they were supposed to be on duty.
Bell was serving a life sentence for murder and was on suicide watch because he had a history of self-harming.
The prisoner ombudsman's report said he had self-harmed 15 times in the four months before his death.
In the days before he died, he tried 73 times to use a helpline in his cell to phone the Samaritans. The line was engaged 63 times.
After he took his life, his body lay in his cell for almost 40 minutes before it was discovered.
In a statement issued by the family of Colin Bell, they said they "intended to take civil action against the NIO and the governor of Maghaberry, and that his death could easily have been prevented".
Prisons Minister Paul Goggins said he had set up a new ministerial forum on prisoner safety.
"There were significant failings at Maghaberry prison and the death of Colin Bell on 1 August last year should not have happened," he said.
"He was a vulnerable and troubled prisoner with a long history of self-harm and while staff did much good work with him during his time in prison, the level of care provided to Colin in his final days was simply not acceptable."
The 44 recommendations from the ombudsman include:
• Prison staff to be made aware of the policies relating to observation cells and self-harm and suicide prevention;
• Prison staff, including night custody officers, to be told that the use of makeshift beds is strictly forbidden;
• Televisions to be removed from all secure pod areas where staff should be monitoring prisoners;
• Staff to be banned from smoking at their posts and from holding other jobs that might affect their performance.