Prosecutors want a noted doctor who breached rules for prescribing ADHD medications to never work again.

GP and attention deficit hyperactivity disorder expert Tony Hanne was before the Health Practitioners Disciplinary Tribunal on Monday, December 18, that will decide his punishment for prescribing drugs like ritalin without the required approval of a specialist.

He maintains without his actions, his patients would never have got the help they needed in a broken system.

But prosecutor Belinda Johns says that's no excuse, that Hanne was dealing with potentially dangerous class B controlled drugs.

"Dr Hanne touts himself as an expert and a leader in the treatment of ADHD but single-handedly dismissed the laws within which such treatment must be provided," she says.

Family doctors can prescribe ADHD medication but each patient must get separate approval from a paediatrician or psychiatrist every two years.

Hanne was successfully prosecuted last year after working with a psychiatrist who effectively rubber stamped the approvals without seeing or speaking to Hanne's patients.

Hanne says at the time, it was to make sure they got the help they needed because many could not access specialist care due to a shortage of doctors - or sometimes the expense.

Johns told Monday's hearing Hanne's behaviour was unlawful and dangerous and if he thought the system was broken, he should have used his position to lobby for change.

"He just chose to ignore what he did not like or agree with," she says.

But Hanne's lawyer Harry Waalkens KC argued it would be gross and unreasonable to stop him from practising.

He's now in his 80s and had transferred most of his patients to other GPs but loved his work and still wanted to keep practising, mainly to give expert advice.

Waalkens says ADHD could have huge consequences for patients, families and communities if left untreated and everything Hanne had done was for his patients.

He notes that, unlike other medical prosecutions, no harm had been done to any patients, instead dozens had written references of support.

Hanne had helped thousands of people over the years, says Waalkens.

"Not one patient has complained, there is not one piece of evidence of anyone being harmed. How can they suggest he be suspended?" he says.

Prosecutor Johns says Hanne showed no remorse or insight that what he did was wrong.

A message needs to be sent to other doctors that bending rules that are in place for safety should not be condoned, she says.

The hearing was adjourned with a decision expected early next year.

-Rowan Quinn/RNZ.