A health trust where 11 deaths are under investigation has been accused of lacking in openness and transparency by the daughter of one of the patients who died.
The daughter of Neil Cormican, who died at Antrim Hospital four years ago, said there had been a catalogue of errors in the handling of her father's care.
The 81-year-old was mistakenly given potassium intended for another patient.
When he died, the trust failed to report Mr Cormican's death to the coroner, despite its obligation to do so, and the family was advised that a post-mortem examination was unnecessary.
An inquest confirmed that his life could have been saved.
The Northern Trust has apologised and admitted its response was below standard.
In a letter dated March 26, it offered an unreserved apology.
"The trust failed to provide acceptable care for your father and, as a consequence of that failure, your father subsequently died," it stated.
Catherine Allen told the BBC that the last four years had been "traumatic and draining".
She added: "It has been very difficult from the outset to find out all the details of what happened to dad.
"There's no other organisation that I know of which if they had caused someone's death would they be allowed to carry out that investigation themselves.
"There has been no openness or transparency – any information that we have got from them, we have had to pursue them for it. Nothing has been forthcoming."
Ms Allen said there was a delay by the trust in reporting the case as a Serious Adverse Incident.
SDLP health spokesman Fearghal McKinney said questions must be asked about how many more deaths were not reported as such.
The latest controversy to hit the health service was yesterday called "the tip of the iceberg" by Stormont health committee chair, Sinn Fein's Maeve McLaughlin.
Health Minister Edwin Poots has said healthcare failures linked to the 11 deaths were not properly acted on.