An Auckland doctor says it would be easy for an unregistered GP to masquerade as fully licensed and get a job treating patients.
Marcus Hawkins, a Botany GP, blames the loophole on weak employment systems and the Medical Council's not requiring photo identification of doctors.
Dr Hawkins passed his medical degree in Britain and worked in New Zealand hospitals for a decade before seeking locum work in general practices for five years. He is now a self-employed GP.
He said none of the clinics that employed him as a locum asked him for details of his New Zealand medical registration or annual practising certificate, although he acknowledged they could have checked with the council without his knowledge.
Michael Clarke, of the Beachlands Medical Centre, one of Dr Hawkins' former employers, said it was routine to check these details, so he would be surprised if this wasn't done in Dr Hawkins' case.
"The only other factor is that sometimes locums come by word of mouth. They might have worked in other practices in the area for a year or two. That was the case with Marcus. He wasn't an unknown face."
Dr Hawkins said that even at his own clinic he had not checked the passports of locums he had hired.
He had urged the council - which controls registration and issues practising certificates - to add photos alongside the publicly available registration information on each doctor on the council website, but it had declined.
He said that without such photo ID, and without routine passport checks by all medical employers, it would be easy for an overseas doctor who was not registered in New Zealand to trick a clinic into thinking they were permitted to practise here.
All they would have to do is learn the name and details of a fully licensed GP in one region and dishonestly name themselves as that person to an employing clinic in a distant region.
If they built a good reputation they would have no difficulty moving from clinic to clinic undetected.
Dr Hawkins said it might have happened already.
"If there's a person masquerading as a second- or third-year medical student I wouldn't be surprised if somebody is doing it as a doctor."
The council said it was the responsibility of doctors themselves - and their employers - to ensure they were fully licensed.