The Prisoner Ombudsman has made 31 recommendations to the Prison Service after an investigation into the death of a prisoner who took an accidental drugs overdose.
Richard Gilmore, 25, died in Magilligan Prison on 11 January 2009.
He had been due for release 19 days later.
Pauline McCabe said the case has again highlighted the serious issue of the availability and use of drugs in prison.
"Mr Gilmore died as a result of an accidental drugs overdose resulting from a combination of prescribed and illicit drugs which had been brought into the prison," she continued.
The report from the ombudsman found that Mr Gilmore had been in prison on previous occasions and prison health records showed that he was known to have a long history of drug problems involving use of multiple substances as well as alcohol.
Several days before he was found dead in his cell, Mr Gilmore, from the Finaghy area of south Belfast, had been home on temporary release.
A fellow prisoner, when interviewed, said the 25-year-old was able to smuggle drugs back into the prison.
Prisoners are subject to drugs tests throughout their incarceration.
On his return from home leave on 9 January 2009, Mr Gilmore undertook a voluntary drug test, which was a condition of his temporary release.
On 15 January 2009, after his death, the result of this test was available and showed positive for cocaine, but no other substances.
At 0223 on 11 January, prison officers entered his cell to find him unresponsive and without a pulse.
Recommendations made by the ombudsman included that random voluntary drug testing is extended to cover all standard prisoners, their frequency should be maximised and a review should be carried out into how cell searches are planned and monitored.
Mrs McCabe also said there should be a review of the level of supervision given to prisoners following serious incidents of drugs misuse and that staff should be reminded of their duty to report any suspected misuse of drugs.
Twenty-one of the recommendations have been accepted, two have been partially accepted and eight have not been accepted.