The HDC reports arrive at a time when the Corrections Inspectorate investigates the death of a Mt Eden Prison inmate on August 13.
The Corrections Department has also taken control of the Mt Eden Corrections Facility, which was being operated by private company Serco, following allegations of fight clubs and drug smuggling.
The Spring Hill case involved a middle-aged inmate, known only as Mr A, who suffered from diabetes and hypertension.
One night, after activating his emergency bell, he was found cold, sweating, and "not very responsive".
Days later he was referred to a public hospital's emergency department and found to have a fractured clavicle and had recently suffered a stroke.
But plans for his post-discharge management were not followed up.
Mr A was hospitalised again a few weeks later with chest pain.
He was assessed and taken back to prison but highlighted issues were not passed on to medical officers.
Weeks later, Mr A was rushed back to hospital where scans showed that he had cancer, which was spreading.
Palliative radiotherapy and care was undertaken but Mr A later died in hospice care.
While the Deputy Commissioner acknowledged that the prison environment "presents certain challenges", she criticised Corrections for its sub-standard care of the inmate between November 2012 and March 2013.
Corrections, who apologised to the dead prisoner's family, today said improvements have been made after the two cases.
"Corrections has a duty of care towards prisoners," said Corrections' offender health director Bronwyn Donaldson.
"Corrections has acknowledged a number of failures in these cases which led to standards of care lower than expected.
"We have taken heed of the Health and Disability Commissioner recommendations and have made changes to address highlighted issues."
