Abuse at a HSE-run care facility in Co. Donegal occurred with the full knowledge of staff and management.
That's the key finding of the Brandon report, which examined a number of serious incidents at St Joseph's Hospital, Stranorlar, from 2003 to 2016.
The resident whose behaviour is the focus of the review was given the pseudonym, Brandon.
A report published by the National Independent Review Panel states Brandon was able to identify particularly vulnerable residents whom he would pursue relentlessly.
It found that management were aware of the sexually inappropriate behaviour by Brandon and the strategy to deal with it was to move him around various wards, which gave him access to other residents, many of whom became new victims.
IN 2011, Brandon was moved into a house on his own on the complex and there was a sharp reduction in the number of sexual assaults recorded.
The report states staff experienced "powerlessness" as they regularly reported incidents up the line in the expectation that something would be done which it says never was.
The report says staff who met the review team described an environment where people "were and still are fearful of coming forward".
The HSE is apologising to residents and their families for the failings in care at the facility.
It says it fully accepts the findings of the report and that it acted immediately once it received it, to seek assurance on the safety of the current residents.