Latest industry figures show clocking – where the mileage is reduced to increase a vehicle's resale value – increased by 10% from March 2015 to October 2015.
As well as defrauding people through higher prices, the crime could hide serious mechanical problems on vehicles and lead to expensive repair bills.
The Local Government Association (LGA), which represents more than 370 councils in England and Wales, is calling for a proposed EU ban on companies providing mileage correction services to be retained under UK laws and brought forward from the current planned date of May 2018.
An existing legal loophole means that while knowingly selling a clocked car without disclosing it is fraud, it is not illegal to alter the odometer's mileage.
It is also calling for mileage correction devices – widely available for sale online for about £120 - to be banned to help reduce clocking.
Fleet News revealed some four years ago that a growing number of vehicles were being handed back at the end of a contract hire or personal contract purchase (PCP) agreement having been clocked.
Council trading standards teams nationwide have helped to secure jail sentences for rogue car dealers and individual sellers in recent clocking prosecutions. They include:
- Five men from the same family were jailed for a total of 18 years and three months for conspiring to clock more than four million miles off cars in a professional car clocking operation. Mileages on vehicles had been lowered by as much as 125,000 miles. The case is believed to be the biggest investigation into car clocking that Birmingham Trading Standards has carried out
- Nottingham City Council Trading Standards investigated two car dealers who were each jailed for 15 months after clocking 13 cars by more than one million miles in a case sparked from a consumer complaint
- A used car dealer was jailed for a year for clocking cars and forging documents in a prosecution brought by Warwickshire County Council's Trading Standards. The case included selling an Audi TT with the mileage advertised incorrectly as 79,000, when it was actually 147,464.
Rogue car dealers and private sellers can increase a vehicle's value by thousands of pounds by reducing the displayed mileage to make them look less well used and more desirable.
For example, taking off 60,000 miles on a Range Rover Evoque or an Audi A3 increases their value by £4,000. Doing the same with a Nissan Qashqai and Volkswagen Golf increases their value by about £3,000 and £2,500, respectively.
But clocking can lead to safety problems, especially if a vehicle appears as if it isn't due a service when it actually is. It could also disguise the need for a major mechanical repair, leaving buyers with a hefty bill if something does go wrong.
Cllr Simon Blackburn, chair of the LGA's Safer and Stronger Communities Board, said: "Car clocking is major fraud that can affect anyone who buys a used car with fake documents, and can have dangerous implications.
"Unsuspecting buyers can be duped into paying over the odds for a vehicle with false mileage and in poorer condition, which could put passengers' safety at risk and lead to expensive repair bills.”
With incorrect mileage displayed, general servicing, which includes brake tests and oil changes, will not be carried out when it is due and may cause vehicle failure. The manufacturer's warranty is also likely to be void if the car is discovered to have been clocked.
Blackburn continued: "Clocking is harming both reputable used car dealers and consumers, and unless the proposed EU ban on mileage correction services is brought forward and made part of UK law, thousands more cars will continue to be clocked over the next two years, jeopardising the safety of cars on UK roads.
"The Government needs to address this and introduce legislation to ban the sale of mileage correction devices, which can only be fuelling the big rise in clocking.
"Trading Standards teams across the country often receive more complaints about used cars than anything else and spend time and resources helping traders comply with the law.
"But councils won't hesitate to prosecute any car dealer or private seller who shows a blatant disregard for safety and consumer rights by clocking cars - they can face hefty fines and a prison sentence, as well as damaging their reputation."
A chauffeur service company is to stand trial for car clocking charges in a case brought by Warrington Trading Standards. Seven individuals from the firm appeared in court in March 2016 to deny the charges, resulting in a trial date being set for 9 January 2017.
RAC head of vehicle inspections Mike Hill said: “It is very difficult to assess the scale of the clocking problem but it certainly appears to be on the increase and the RAC has been working with local trading standards to tackle the issue.
“One reason for the growth could be the number of private cars now bought under PCPs Personal Contract Purchase which may tempt some motorists to use a clocking service or even purchase the equipment to do it themselves to avoid a fine for exceeding the specified mileage in their contract.
“However, it is a practice that is usually employed by unscrupulous car dealers who will use a number of techniques to pass off a high-mileage vehicle as something that it isn’t – increasing the list prices by hundreds if not thousands of pounds.”
Hill concluded: “The RAC would like to see mileage correction devices banned from sale and is calling on the Government to review current legislation to make it illegal to physically wind back the mileage of a vehicle to protect the rights of used car buyers.”