A man allegedly used fake documents to secure a job as a doctor at one of the country's busiest hospitals where he saw dozens of patients.

Stuff understands the man worked in the respiratory department at Middlemore Hospital in south Auckland for several months, before it was recently discovered he was not in fact a registered doctor.

Te Whatu Ora Counties Manukau has confirmed it filed a complaint to police who are understood to be investigating.

A spokesman for the organisation says the man was employed in February 'on the basis of documentation that was not authentic”.

He worked in a 'clinical research position”, was no longer employed by Te Whatu Ora Counties Manukau and a complaint has been made to the police, the spokesman says.

Stuff understands the man was employed on the basis he was a doctor. In his role at the hospital he examined dozens of patients.

It is thought the man is not registered to work as a doctor in New Zealand.

Health Minister Andrew Little says he was advised on Wednesday that a staff member at Middlemore was stood down last week following 'concerns about his qualifications”.

'I have been advised that an investigation is under way into the actions of this person.”

Te Whatu Ora Counties Manukau, formerly Counties Manukau District Health Board, cares for a population of about 600,000 people across south Auckland, as far as Franklin.

The organisation employs more than 9000 staff.

Middlemore suffered from staffing shortages as recently as June with Covid-19 and winter bugs taking their toll on staff and the community.

Te Whatu Ora Counties Manukau did not address questions from Stuff about the vetting process the man went through, how his alleged deception was discovered and whether the organisation had contacted patients seen by him.

A police spokesperson confirms an investigation is under way, but says they can't comment further.

-Stuff/Blair Ensor and Edward Gay.