CAR owners are increasingly being threatened with court action over disputed parking charges as more private firms pass outstanding tickets on to debt collection agencies, a consumer watchdog has warned.

Citizens Advice Scotland has said the number of people concerned about getting a letter from a debt agency over parking fines has risen from zero last year to 100 in the past few months.

The letters seen are all sent by specialist parking recovery, investigation and enforcement bailiffs Debt Recovery Plus Ltd - and demand payment for tickets sometimes in excess of £100.

A £100 fine is the suggested maximum that the two industry bodies - the British Parking Association and Independent Parking Committee - say should be allowed to be charged.

The BPA code of practice also says that if the charge is more than that a firm must be able to justify the amount in advance.

And the IPC say warnings about the reference to the prospect of additional charges, should be made on signs and in associated documentation.

The letters go on to say if payment is not made the company will “recommend to the creditor that court action should be taken to recover what you owe.”

DRP Ltd say an original charge will never be for more than £100, reduced to £60 if paid within the first 14 days, and fees are only added after action by the operator has resulted in a non-payment of the charge.

The firm said local authorities also add fees and charges where a parking ticket issued by them remains unpaid.

CAS consumer spokesman Fraser Sutherland said: “We have recently seen evidence that Debt Recovery Plus Ltd have been sending letters to people who have had a parking ticket issued by a private parking firm for alleged infringements in places like supermarket car park or hospitals.

“It’s important that drivers check signage when parking to know their rights and responsibilities while using that car park. However recent debt collection letters obtained by CAS show that fees in excess of £100 are being demanded. This is in clear breach of the parking industry’s own self-regulation code.

“These examples are more evidence that self-regulation in the industry is not working, and that 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 our 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.”

A DPR Ltd spokesman said: "We operate under and comply with both British Parking Association and Independent Parking Committee codes.

"Both codes allow for debt recovery action AFTER the parking operator has unsuccessfully tried to collect a parking charge."

CAS pointed to December court appeal by a British motorist against a private parking charge which found that a charge of £85 was reasonable but only if brought clearly to the attention of the motorist at the time of parking.

The ruling judges used the £100 "maximum" set by the BPA in deciding that £85 was not extravagant, CAS said.

A CAS ‘Its Not Fine’ campaign was launched last year to inform consumers about their rights when using private car parks, encourages them to challenge unfair treatment.

In July, CAS said the number of people seeking help on the issue of fines imposed by private car parks had risen by 45 percent in a year.

The numbers seeking advice on the issue was 4,000 in February 2013, but had risen to 25,000 in March 2015.

The It's Not Fine campaign found that private car parks often do not have clear signs showing their fees, and that many firms were using aggressive and misleading tactics when pursuing debts.