The residential care employee was also criticised by the Deputy Health and Disability Commissioner for failing to intervene when she was self-harming.
The ill-treatment came to light when a complaint was laid with the Health and Disability Commissioner (HDC) over the woman's rights being breached by being recorded without her consent.
"The woman was living in a disability residential care setting, and had multiple complex social and mental health disorders, which could manifest in challenging behaviours and actions," the HDC said in a release.
"The interactions between her and the support worker at the centre of the investigation, where the support worker could be heard being verbally abusive and spitting at her, were recorded on video."
The content of the video sparked an investigation into the support worker's actions.
"The complaint may never have been brought to the attention of this office had it not come to light in another complaint investigation," said deputy health and disability commissioner Rose Wall.
"I consider this complaint is significant, as it raises concerns about a longstanding support worker's verbal maltreatment of a vulnerable consumer with dual disabilities and challenging behaviour in residential care."
Wall said the video showed the support worker provoking and insulting the woman "which amounted to a serious lack of respect", and failing to step in when she was self-harming.
"There were many options available to [the worker] to intervene, including talking to [the woman], employing de-escalation techniques he had learned in non-violent crisis-intervention training, and/or calling for assistance. He did not attempt any of those actions or any other type of intervention."
Wall said she was "appalled" and "under no circumstances" would his behaviour be acceptable.
It was determined the worker breached rights one and three of the Code of Health and Disability Services Consumers' Rights - not treating her with respect or dignity.
Wall recommended the worker - who was no longer employed at the care facility - make a formal apology, and for any future employers to put him "put him through training on treating consumers with respect and dignity and relationship management/communicating with people who display challenging behaviour".
