A patient whose teeth were pulled out by mistake and two patients given 10 times the correct dose of medicine are among the latest list of 258 hospital botch-ups.
At least 76 people died from preventable mishaps in their hospital treatment in the year to last June.
The previous year, the first time such figures were made public, 40 people died from 182 preventable mishaps.
The cases of mistaken identity and medical mix-ups were released by the Ministry of Health's Quality Improvement Committee (QIC) yesterday using reports from the country's 21 district health boards (DHBs).
The health watchdog said the list could be greatly reduced if all hospitals used the same set of checks.
QIC chairman Pat Snedden said the rise showed hospital staff were getting better at admitting mistakes as DHBs trained their staff in reporting.
But Health and Disability Commissioner Ron Paterson said encouraging hospitals to report their errors was useless unless all DHBs adopted good systems for prevention.
"The sort of things uncovered in these reports are not news to me, and they are not news to DHBs," he said.
"What families want to know and what the public of New Zealand wants to know is that concrete steps are being taken to prevent this sort of harm.
"Frankly some of the actions and responses are relatively weak, because simply to say you have increased staff education doesn't solve the problem."
Reporting is voluntary and DHBs do not know how many mishaps go unreported.
Serious or life-threatening errors represent a tiny proportion of the almost 900,000 patients treated and discharged by public hospitals in the year to June.
Auckland City Hospital reported 30 serious events, including one patient who had all their teeth removed when they should have lost only some teeth after their referral letter was scanned into the system under the wrong name.
In another case, a Counties Manukau DHB patient was booked, checked and anaesthetised for eye surgery before it was noticed they had already had the operation at another hospital.
Auckland City Hospital anaesthetist Alan Merry, who has just finished running a successful trial for the World Health Organisation (WHO) to reduce cases of mistaken identity, said it was distressing to read about patients who were mixed up with someone else in the operating room.
Mr Merry wants the checklist piloted at Auckland City Hospital rolled out around the country.
Mr Paterson agreed the WHO checklist should be standard in all hospitals - but said as yet there were no plans to take the pilot nationwide.
Mr Paterson also wants safer medication practices to become standard for all DHBs, to prevent cases such as one at Counties Manukau where a patient had to be given an antidote after getting 10 times the required dose of morphine.
Falls in hospital - which made up 28 per cent of the serious events in the latest report - are another area DHB representatives said could be the subject of national prevention standards.
Canterbury had the highest number of serious and sentinel events, with 41, up from 22 last year.
Counties Manukau had 23, up from just three last year.
Mr Snedden said the numbers would continue to rise as DHBs were trained to better report incidents.
Mr Paterson said he was more concerned about the drop in reported events at Waitemata DHB - down from 22 events last year to 11 this year - than he was about DHBs whose reported events increased.