Four opportunities were missed to diagnose an inoperable brain tumour in a prisoner who died less than two months after he was released.
The Prisoner Ombudsman said earlier diagnosis would not have saved him.
However, it found measures to extend his life expectancy and reduce his distress through earlier palliative care could have been provided.
The man, known as Mr H, was released at the end of July 2014 because of his condition, and died in September 2014.
The ombudsman’s investigation found that some of Mr H’s care had been very good, and several prison officers and nurses had shown compassion for him while he was in Maghaberry jail.
It said that he was not always compliant with the care that was offered and it was possible that his attempts to manipulate his prescribed medication did not assist his diagnosis.
Treatment was also delayed when he did not attend a hospital accident and emergency department, it found.
However, the ombudsman also found that care plans were not initiated when Mr H became dehydrated and malnourished.
It has made 15 recommendations for improvement, which have been accepted by the South Eastern Health and Social Care Trust and the Northern Ireland Prison Service.
The trust, which looks after healthcare in Northern Ireland prisons, said it was committed to implementing improvements as a result of the lessons learned from all investigations.
The Prison Service said it was determined to use this report to strengthen systems already in operation throughout Northern Ireland’s jails.
Prisoner Ombudsman Tom McGonigle said: “This report again highlights the need for someone to actively take charge and manage the first line clinical care of patients in prison, where families are less able to assist or advocate on their behalf.
“The fact that we also published a report last week which raised virtually identical issues, reaffirms the need for the prison healthcare reform project to provide improved diagnoses and better palliative care for the terminally ill.”
A solicitor for Mr H’s family said the report “makes concerning reading”.
Katie McAllister of Madden and Finucane Solicitors said: “The family are considering all options at present, including the possibility of issuing proceedings for the negligent treatment of their son.
She added: “We have to hope the prison will act in good faith and implement these changes.
“We have seen similar recommendations in the past and the situation hasn’t improved vastly, there are still major issues with prison health care.”
The prisoner’s father said: “Our family welcomes the findings of the prisoner ombudsman report and we hope that the authorities can learn from the mistakes made in my son’s case in order to prevent another family having to go through a similar ordeal.”