The Health Quality and Safety Commission says instances of harm to patients in public hospital will continue to rise for the next two or three years while staff grapple with improving safety in the longer term.
The commission has issued a report on potentially preventable events in the past year.
It was the fourth annual report on incidents that either did or could have harmed patients and which could have been prevented.
In the year to June, 374 people were involved in such events and 217 later died. There were 92 deaths the previous year.
The commission says public hospitals were safe for most of the almost one million people treated in the past year.
Falls, clinical management problems and suicides were the three most commonly reported problem areas.
The commission says increased awareness is behind the rise in reported cases.
Canterbury District Health Board chief medical officer Nigel Millar, says staff are no longer quite as nervous about reporting failures as they were at the start.