The door's ajar for a wider inquiry into the Waikato District Health Board and its mental health unit.

It's now subject to a formal inspection by the Director of Mental Health following allegations the DHB hired a fraudster who'd managed to pass himself off as a psychiatrist.

Minister of Health Jonathan Coleman tentatively said there is scope for a broader inquiry to be carried out.

"Well, it would take recommendations from the inspection, so let's just wait and see then."

Labour's Hamilton MP Sue Moroney said the review will show the systemic problems that exist.

"I think the DHB have had their own head in the sand and so it'll be very interesting to see what comes out of that formal inspection."

Meanwhile the Medical Council of New Zealand is confident it followed the right steps when registering a man accused of faking being a psychiatrist.

Council Chairman Andrew Connolly said he'd reviewed all the rigorous processes the council has in place.

He is completely reassured they've followed the right steps in this case, "but that raises the question - how did this doctor gain registration?"

Mr Connolly said to register as a doctor, a person requires original documents, not copies.

"But if someone has used those falsely, how did they obtain those documents in the first place? There are a number of questions that we just cannot answer at this point."

He said it's very difficult to forge such a document, but "it's not unheard of around the world."

"The last known case we can identify in New Zealand was around 1997/98."