A doctor who prescribed morphine to a man addicted to opiates and addictive painkillers to four other patients has been found guilty of professional misconduct.

The Health Practitioners Disciplinary Tribunal censured the doctor, whose name is permanently suppressed, and ordered him to continue seeing a psychologist, continue to be mentored by another doctor and to pay $24,000 towards the cost of his prosecution.

In the case of the man addicted to opiates the tribunal said the doctor knew the patient was addicted "but mistakenly assumed that (the addiction) would not be too difficult to cure" and that "he could help this guy".

The doctor believed by treating the patient himself he would able to keep him off a benefit and in work.

The tribunal said the doctor was not authorised to prescribe morphine but had gone ahead with the illegal treatment, and this was exacerbated by the fact that it continued for over two years.

In the case of a patient with rheumatoid arthritis, the doctor admitted that between 2008 and mid 2010 "I allowed (the patient)to drift down the slippery slope of using regular Pethidine tablets and injections to control pain".

The tribunal found that while the issue was complex and the patient difficult to manage the continued used of an addictive opiate was not appropriate.

In the case of this patient and of his wife, who was treated for bilary colic, the tribunal also found that prescribing self injectable Pethidine was negligent.

The tribunal found that across all the patients there was a pattern of inappropriate and excessive prescribing of addictive drugs.