Concern has been raised over an alleged 'fake taxi' which attempted to pick up passengers in Dundee on Saturday night.
Posts on Facebook by taxi driver Jim Harris allege that a taxi was operating without a licence in the city centre.
He said a group of girls told him the driver in question said he was working freelance and had shown them a 'fake' taxi badge at a rank outside Dundee Contemporary Arts (DCA).
Mr Harris reported the incident to police with the force now investigating.
He said: "It's very serious. Not having a taxi plate is a red flag straight away.
"All sorts of things were going through my head. He could be anybody."
Graeme Stephen, chairman of Dundee Taxi Association, said he had not heard about the incident but said it was a "serious matter".
"It's quite concerning," he said.
"Imagine he had picked up passengers and then something had happened then this driver could face problems.
"You have really got to be careful."
Mr Stephen said this is the not the first time he had heard of reports of unlicensed taxis operating in Dundee.
He added: "There were reports of an unlicensed taxi operating around a year ago picking up passengers at the bus station.
"It was escalated but I'm not sure what was done about it in the end."
A police spokesperson said: "Police Scotland can confirm that it received a complaint from a Dundee taxi driver on Sunday January 28 in relation to a potentially unlicensed taxi operating in the city centre.
"Enquiries are ongoing into any potential licensing issue."