A Canterbury doctor has been found guilty of disgraceful conduct after having sex with a teenage rape victim 25 years ago.

The GP, identified only as Dr C, twice had sex with the complainant, Ms A, in March 1985, when she was 16-years-old, the Medical Practitioners Disciplinary Tribunal said in a decision released today.

Ms A had been receiving informal counselling and support from Dr C after she complained of being raped by another man.

She also regularly babysat Dr C's children at his home - where both incidents of sexual intercourse occurred.

The tribunal heard the case during a four-day hearing in Christchurch last year, where it was debated whether Ms A was Dr C's patient at the time of the offending.

The tribunal today said it was satisfied there was a doctor-patient relationship when the sex happened and Dr C's conduct was disgraceful and warranted "a disciplinary sanction".

He continues to practise and has interim name suppression.

Ms A was an honest and reliable witness and Dr C exploited a vulnerable teen, the tribunal said.

"Dr C himself must have known she was at risk - this required him to be more concerned for her welfare, not exploiting her vulnerability for his own gratification. The fact that she babysat his children was a further reason why he should not have taken advantage of her," it said.

"The fact that she turned to him for comfort and solace following the rape only highlights her need for protection, not exploitation. In short, there was both a power imbalance and exploitation."

The tribunal will release its decision on Dr C's disciplinary action in August.