An investigation has been launched after a parking attendant was caught putting up a temporary "no parking" sign before issuing a ticket.
He then took the sign away and the car's owner was sent a Parking Charge Notice for £100, the BBC has found.
UK Car Park Management Ltd issued the notice as part of its "self-ticketing" scheme which pays landowners £10 for reporting parking infringements.
The firm said it believed the incident in Cardiff was isolated.
A lawyer who is an expert in parking law told BBC X-Ray the man was acting "fraudulently".
"In my opinion he is engineering that situation, he's receiving monies off the back of deceiving the parking management company which, in essence that's fraud, it's a fraudulent act," said Cardiff-based Sarah Garner of DAS Law.
"It's completely wrong and it should not happen," said Will Hurley, chief executive of the parking regulator the International Parking Community (IPC).
The ticket was issued by former Welsh boxing champion turned parking entrepreneur Peter Ahmed - who runs a car park near Curran Embankment in Butetown, where the notice was issued.
The Parking Charge Notice (PCN) was given to Kelly Venables from Wenvoe near Cardiff while she was Christmas shopping with her family.
She had parked in the lane before because there were was nothing to indicate it was forbidden.
Two weeks later she got the PCN in the post, complete with a photograph of her car "with a big sign behind it".
"I knew that sign wasn't there, there was no way you could miss that sign," she said.
"And there was absolutely no way I was paying it, there was no way I was just going to let it lie."
When she found footage on a nearby CCTV camera, she saw that Mr Ahmed had put up the sign just so he could take a picture of her car and issue the penalty notice.
"I can't believe that somebody can be quite so dishonest. I can't believe that practices like that are allowed by supposedly regulated car parking firms," she added.
UK Car Park Management Ltd (UKCPM) operates a "self-ticketing" scheme, which allows a landowner or agent who signs a code of conduct to use an app on their phone to send details of illegally parked cars.
The firm obtains the owners' details from the DVLA and issues a parking charge to the driver, and the agent gets £10 for every ticket they issue.
Peter Ahmed had signed up to this scheme - but has had his account suspended after X-Ray uncovered the way he had issued the PCN.
Mr Ahmed told the programme he did not have enough signs so had used a "mobile sign" until new supplies arrived.
He said he thought he was within his rights to do so because there were other signs in the area. Mr Ahmed said he now realised this was not acceptable and apologised.
UKCPM said it had launched its own investigation and had cancelled the PCN as soon as they became aware of what had happened.
Mr Hurley added: "We will now look into it and what went wrong and when we get to the bottom of that we will be able to look and see what needs to happen moving forward.
"But the fact that this happened in the first place indicates that something needs to be done to ensure this does not happen again."
The DVLA said it had taken "immediate action" alongside the IPC to investigate the incident.
UKCPM said it believed this was an isolated occurrence.
"There's a good indication that it is a one-off incident and it's isolated. However, we will look at it with an open mind," Mr Hurley said.
X-Ray is on BBC One Wales at 19:30 on Monday and on iPlayer afterwards.