Shortcomings in the care given by the Hutt Valley District Health Board ended in the death of an 11-month-old baby.
The finding has been made by Health and Disability Commissioner Anthony Hill.
The baby girl was admitted to hospital in 2010 with vomiting, poor weight gain and other issues. She was cared for by a team including a paediatrician and a dietician, and fed with a concentrated infant formula.
The baby improved initially but then caught rotavirus and died soon afterwards from factors linked to renal failure and a high concentration of sodium in her blood.
Mr Hill said on Monday that extra monitoring and other changes were needed after the rotavirus diagnosis, but key caregivers were not aware of the infection.
He said the sub-optimal care is the responsibility of the board, which has apologised.