The country's largest provider of disability and home-based support faces legal action over the care given to a severely disabled woman.
The public health watchdog says failures by Healthcare of New Zealand Limited were totally unacceptable. The organisation now faces a Human Rights Review Tribunal hearing.
The case involves a Nelson woman paralysed from the chest down who lived at home alone.
Listen to Rose Wall
Deputy Health and Disability Commissioner Rose Wall said the woman gave six months' notice that her usual caregiver was taking leave and alternative care would be needed between 29 December 2012 and 6 January last year.
No one was found, and she was left alone, struggling mentally and physically for four days.
Just a week before, the woman had been left on her own for two days and one night. She emailed a nurse at Healthcare New Zealand, describing her tears and frustration at lying in filthy sheets and her struggle to shower herself.
For the past 12 years, Healthcare of New Zealand has been funded to provide the in-home care during the day and sleepover shifts. Ms Wall told Radio New Zealand's Checkpoint programme that it failed in her care.
"A woman who was paralysed from the chest down, no family or access to friends nearby, was reliant on this organisation to support her on a day-to-day basis."
Healthcare New Zealand chief executive Peter Hausmann has issued a statement saying the company accepts the findings by Ms Wall and is deeply sorry for what happened.
Mr Hausmann said they have apologised to the woman in person, respect her courage and determination to live her life independently, and are doing everything to ensure that this never happens again.
ACC has also put out a statement saying Healthcare New Zealand's failings are totally unacceptable.