Health staff are due about $450 million in holidays and many have more than four weeks of leave owing.
Leave owed to staff has increased according to official figures and comes at a time when some district health boards say they will meet savings targets through not filling vacancies.
Health Minister Jonathan Coleman has refused to comment on an issue his spokeswoman said is "operational", a response his Labour counterpart Annette King has labelled "cowardly".
She said the figures - sourced by Labour through the Official Information Act - show health staff are carrying the system.
The almost-half-billion dollars in leave owed to staff for holidays came to light after the Herald revealed district health boards were under pressure to save at least $138 million this financial year.
The focus on savings at health board level has been a feature of health management since the creation of Health Benefits Limited, a government quango charged with making $700 million savings in five years. It closed in 2015 after the auditor general found it was directly responsible for $71 million in savings.
Health board savings plans include banking cash from not replacing staff and - at one health board - reducing the amount of cancer treatment.
Auckland health board has the largest debt to staff, owing 9539 staff about $72 million in holidays. Of the staff owed holidays, 40 per cent are owed more than four weeks.
The other Auckland health boards - Counties Manukau and Waitemata - are also heavily indebted to their staff, but MidCentral health board has the highest number of staff owed long periods of leave.
At MidCentral, which provides health services in the Manawatu, 52 per cent of its staff are owed more than four weeks leave.
The figures for many DHBs appear higher for government departments whose leave balances are collected by the State Services Commission, which measures on the basis of five weeks or more owed.
The Ministry of Foreign Affairs and Trade led 2014 figures with 39 per cent of staff owed more than five weeks. The Department of Corrections was close behind on 37 per cent. Most departments had much lower levels. Only 6 per cent of staff at the State Services Commission were owed more than five weeks leave.
Mrs King said the holidays statistics were linked to DHB plans to make savings through gaps in staff. It meant those staying in the jobs were unable to take holidays because they were covering for positions which had not been filled.
She said Mr Coleman set the funding which led to staff not being replaced and the amount of holidays owed to staff ballooning. "For him to run away from this issue is very cowardly. I think DHBs are doing the best they can, but he refused to front up to the issue."
Public Service Association national secretary Erin Polaczuk said staff spoke of asking for leave and being refused. "Everyone was entitled to leave and should take it."
Requests to Mr Coleman for an interview or statement were rebuffed. The issue was "operational", said a spokeswoman, and was for health boards to offer comment.