The Nurses Organisation says nurses are forced to make ethical decisions about the kind of care they can give patients because of inadequate staff numbers.
A report from the Hutt Valley and Wairarapa District Health Boards says nursing staff numbers are tight and 'care rationing' is sometimes used, where essential care is prioritised over patient comfort.
That could mean patients may not be bathed, changed or have their hair brushed. The report says, however, such incidences are very rare.
Associate professional services manager Hilary Graham-Smith says care rationing is widespread in New Zealand hospitals.
Ms Graham-Smith says a lack of resources and staff means important patient care is sidelined.
She says care rationing is not limited to activities such as washing people, but also includes delivering medications on time, and assisting patients to walk.
She says there is a strong association between inadequate staffing levels, care rationing, and poor patient outcomes.
Chief executive for both boards, Graham Dyer, says sometimes nurses call in sick and patient demand is high.
He says on those days, patient needs such as hydration, medication and airway management are prioritised and some comforts might fall by the wayside for a few hours.
He says the practice is about making sure patients get what they need and reducing patient care is the last option when resources are stretched.