The number of preventable injuries and deaths in public hospitals rose by almost a fifth in the year to June 2011.
A Health Quality and Safety Commission report shows 377 serious and sentinel events were reported in the period, compared with 318 in the previous fiscal year - a rise of 18.5%.
In 86 of the 377 cases the patients died.
Of the events reported, 195 were falls, 60 more than in the previous year.
There were 108 management related errors, including delays in treatment, diagnosis and poor communication between health professionals.
In one example of poor co-ordination, a baby was stillborn after an ultrasound scan request form was not sent.
The planned induction date was missed and there was a delayed caesarean section.
The commission's chair, Alan Merry, says the patients who were injured or died in the 377 events were let down by the health system and many of the cases should have never happened.
He says work is being done to prevent and reduce harm from falls.
Some 2.7 million people are treated in public hospitals each year.