The ACT Civil and Administrative Tribunal said controversial neurosurgeon Raymond Newcombe operated on the wrong part of one patient's brain using inappropriate instruments.

The tribunal said Dr Newcombe failed to exercise professional judgment and failed to conduct himself in a way that maintained public safety.

In a judgement published yesterday, tribunal president Linda Crebbin and two senior members declared that if the neurosurgeon had been registered to practice, he would have breached professional standards and would have been unsuitable to practice. Dr Newcombe retired a decade ago.

The tribunal found Dr Newcombe failed three patients, though it cleared him of misconduct in the case of a fourth patient. In the case of one patient, known only as L, the tribunal said Dr Newcombe did not realise he was, or could be, operating in the wrong part of the patient's brain.

He was also using the wrong instruments for the operation and failed to provide L with adequate post-operative care.

''The tribunal is satisfied that the respondent's breach of the required standards of practice in relation to L, fell so far short of the required standards that it demonstrated a lack of competence to practise,'' the members wrote.

They also found Dr Newcombe failed to ensure accurate clinical records about another patient, known only as S, and tried to cover up an ''adverse event'' suffered by S.

A third patient, known as O, underwent spinal fusion surgery but the tribunal ruled Dr Newcombe had failed to confirm the surgery was conducted at the correct level and failed to keep accurate records about the operation.

The tribunal cleared Dr Newcombe of impropriety in the case of a fourth patient known as D.