Health Minister Tony Ryall says no one knows the exact number of patients who have been harmed in public hospitals.
The Ministry of Health issued its second report on serious and sentinel events on Tuesday, detailing errors that affected 258 patients nationally; 76 patients died.
Errors reported the previous year affected 182 patients, 40 of whom died.
Mr Ryall says the latest report reflects the health service being open and upfront. He expects the figures will increase again next year as the reporting system becomes more accurate.
Health & Disability Commissioner Ron Paterson says the examples cited in the report make for sobering reading.
He told Morning Report that he commends district health boards and clinicians for making the information public, because people need to know what's happening.
He said progress is being made in areas like medicines reconciliation to reduce the scope for errors, but gaps still exist and more could be done.
Figures from all district health boards are on the Ministry of Health's website.
