A family doctor who continues to see patients has been accused of exploiting and threatening a vulnerable female patient he had sex with more than 30 times.
The GP may face legal action and it is alleged he sent her more than 600 sexually explicit messages toward the end of the year-long relationship.
In a report released on Monday, Health and Disability Commissioner Anthony Hill said the unnamed doctor showed a flagrant disregard for patient rights.
Mr Hill said the woman in her mid-30s felt threatened and unable to refuse the demands made in 2010.
The doctor has denied the allegations, but Mr Hill said there is sufficient evidence from cellphone records and a separate police inquiry.
"Doctors have a relationship of trust and this doctor did not respect that. I think his behaviour was a very severe departure from what is expected in New Zealand and I'm very sure that his colleagues view it in exactly the same way."
Mr Hill has referred the case to the Medical Council and to the independent legal arm of his own office for possible action.
The investigation began after the commissioner received a complaint by the unnamed woman about the sexual relationship with her GP.
The relationship began when the woman visited the doctor's surgery one evening to collect a prescription for her husband.
Mr Hill said there were over 30 sexual encounters and the doctor threatened to tell the woman's husband if she refused. Near the end of the relationship, it is alleged he sent her more than 600 explicit text messages.
Medical Council chair John Adams said on Monday it is looking into the case urgently.
"We will be taking action to consider the information the (commission) has provided to us and the options that we have in front of us to investigate this practitioner further, and use the sanctions possible under the act, depending on the risks that we identify to the public."