It is alleged 10 staff or relatives of staff presented to Colac Area Health's urgent care department within half an hour on August 9 when Health Minister Mary-Anne Thomas toured the hospital in the state's southwest.
All 10 of the allegedly fake urgent care arrivals were recorded in the hospital database, before being cancelled without being discharged after the minister left, the Colac Herald reported this week.
Ms Thomas said her department has appointed an external investigator to probe the claim.
She promised communications between her office and the hospital would be made available to the investigator and confirmed no request was made to the hospital to make sure the clinic was busy for her visit.
"Of prime concern to me is what, if any, impact did these so-called fake patients have on the ability for real patients to receive care on the day?" she told ABC radio on Friday.
"I have never seen or heard of anything like this before."
The investigator will prepare a report which will be handed to the health minister.
Ambulance Victoria is separately investigating the allegation.
An anonymous whistleblower first made the allegation to the Victorian Public Sector Commission in late August, and the minister and her office were notified.
It was then referred to the Independent Broad-based Anti-corruption Commission and the Victorian Ombudsman, both of which declined to investigate further.
State Opposition Leader John Pesutto on Thursday expressed concern about the incident calling for a retired judge or body independent of government to take over the probe.
But a member of his shadow cabinet and local MP Richard Riordan defended the hospital's practices.
"That they brought community members, people who are working not only in the organisation, but received the service of it, have helped and worked with the agency to demonstrate capacity constraints? Yes, that's okay," he told ABC radio.
Colac Area Health covers about 30,000 people in the Corangamite, Colac Otway and Surf Coast Shires.
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