Investigators are examining claims the city council has doled out thousands of unlawful parking tickets in Canterbury, Whitstable and Herne Bay.

A UK-wide motorists’ watchdog has referred the authority’s enforcement policy to the district auditor claiming “long-time serious irregularities".

National Motorists’ Action Group (NMAG) says that parking signs throughout the district are illegally worded and rely on a misinterpretation of the law.

If the auditor agrees, its findings will heap pressure on the council to refund fines totalling hundreds of thousands of pounds.

NMAG has a proven track record of successfully challenging local authorities over dubious parking policies.

In one instance, the London's Newham Borough Council buckled under pressure and refunded £350,000 raked in from unlawful fines.

NMAG director Peter Ashford said: “Canterbury City Council, like every other enforcement authority, is required to be conversant with all relevant parking legislation and should have known years ago that its parking signs are basically home-made inventions that are not lawful traffic signs.”

Earlier this month, KentOnline revealed how a landmark tribunal ruling found the city council guilty of illegal parking enforcement in one of its Canterbury zones.

Julie Chandler had appealed against a ticket handed out after moving her car from one space to another within the St Lawrence zone near Kent and Canterbury Hospital.

An adjudicator ruled against the council, finding that a ‘no return’ rule can apply to a parking space but not to an entire zone.

Despite the ruling, the city council vowed to continue with its existing policy and leave the signs unchanged.

"Canterbury City Council should have known years ago that its parking signs are basically home-made inventions that are not lawful traffic signs..." - NMAG director Peter Ashford

But NMAG’s legal experts now believe the extent of the council’s alleged wrongdoing goes much further.

The group claims all parking enforcement based on the district’s parking zones is unlawful.

If true, all tickets slapped on cars for infringements linked to parking zones within Canterbury, Herne Bay and Whitstable could be called into question.

It is thought the district’s parking zone policy dates back to 2008, and NMAG’s claims could therefore affect thousands of motorists.

According to NMAG, Canterbury City Council has misinterpreted the relevant traffic order which lays down its powers of parking enforcement.

The order states that the zones can only exist “for the purposes of administering residents’ parking schemes”, says NMAG.

It argues that parking zones cannot therefore exist for the purposes of parking enforcement.

In a detailed report submitted to both the council and the district auditor, NMAG states: “There are no parking zone areas established by the Canterbury traffic order.”

The report, submitted to the city council chief executive, concludes: “The entirety of the parking signage... throughout the roads related to the Residents’ Parking Scheme zones is unlawfully in place on the public highway and, therefore, cannot enable lawful enforcement.”

NMAG is calling on the district auditor to investigate.

It wants Canterbury City Council to amend its signage and policy and, crucially, to seek all drivers unfairly ticketed and refund them.

The council’s district audit is carried out by legal practice Grant Thornton LLP and its consideration of the report could take months.

However, if it were to agree with the arguments within the report, the auditor could also call on the city council to refund the fines.

Further refusal by the council could result in the issue being taken to judicial review.

City council spokesman Rob Davies said: “We have received this and have replied to acknowledge it. We’ll look into the issues that have been raised and will reply fully in due course.”