The Public Service Association is hitting out at funding shortages at district health boards, amid claims patient care is being jeopardised.
There are reports of hospital staff being unable to take breaks or holidays as vacancies aren't filled, so money can be saved.
Analysis by the Council of Trade Unions suggests DHBs have a funding shortfall of around $116 million.
Public Service Association National Secretary Richard Wagstaff says health needs to be invested in, not neglected.
"Health is always going to be a very demanding sector," says Mr Wagstaff. "There are increasing demands on it for a number of reasons, including an aging population.
"We can't just wish it better but spend less – we have to maintain investment and we haven't been doing that."
Mr Wagstaff says overworked and stressed clinical staff will only mean that patients suffer.
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