Nearly 400 motorists from across Tayside have sought advice after being landed with charge notices from private parking companies in the last year.
And many of them have been threatened with court action by debt collectors for not handing over their cash.
Citizens Advice Scotland (CAS) said it was approached by 370 people at its Tayside branches who were having issues with private parking firms.
Research from the organisation found a number of those people had been threatened with court action by debt collectors hired to pursue drivers who do not cough up.
One Dundee lawyer said the situation in the city is as bad as he has ever seen it.
Fraser Sutherland, the consumer spokesman for CAS, said: “Self-regulation in the industry is not working, and many car-parking firms are flouting their own regulations with a gung-ho attitude of simply collecting as much as possible from drivers.
“Citizens Advice Scotland will continue its campaign for better controls on private parking companies to ensure that they comply with consumer protection regulations.
“We also urge consumers to contact us for advice if they feel they have been unfairly treated by a private car park or if they have received one of these debt collection letters.”
Dundee solicitor Gary McIlravey, who said he had taken on several cases relating to private parking charges in the last year, said the debt collectors’ letters are a “red herring” to frighten people into paying.
He said: “The issue with private parking fines in the city is the worst I have ever seen.
“When court action is threatened through these letters, there has to be a court order but most of the time these debt companies don’t necessarily have one.
“The letters are a bit of a red herring they are there to try to frighten people into paying the fine.
“It’s the parking company who can take the matter to court, so it is always useful to seek legal advice before deciding to argue against the fine or simply not pay the fine.”