The number of motorists handed parking fines by private companies soared by more than a quarter over the past 12 months, new figures indicate.
RAC Foundation analysis of official data showed that 4.71 million of the DVLA's vehicle keeper records were obtained by parking management firms in 2016/17, up 28% on the previous year.
The majority of this information is likely to have been used to send penalty charges worth up to £100 to drivers who allegedly infringed parking rules, the motoring research charity said.
The data suggests a parking ticket is issued every seven seconds in Britain.
Clamping on private land was banned in all but exceptional cases in 2012 by the Protection of Freedoms Act.
But the Act also allowed for private parking companies to pursue the registered keepers of vehicles they claim have infringed their rules, rather than having to prove who the driver was at the time of the incident.
In 2012/13, only 1.89 million records were obtained by private companies from the DVLA, according to the analysis.
RAC Foundation director Steve Gooding said: "These numbers are eye-watering.
"We all hoped the problems associated with parking on private land would go away when clamping was outlawed.
"It turns out we hoped in vain. Since the ban there has been a surge in ticketing. Something is clearly going awry.
"Of course the rights of private landowners need to be protected, but where landowners invite people to park on their property, often to benefit from their trade, the rules need to be fair to both parties.
"Time and again we hear stories of people who feel that the terms were unclear, the tone of communication intimidating and the price of even the shortest accidental overstay extortionate."
A consultation on changes to regulations for parking on private land was launched by the coalition government and ran until May 2015.
Mr Gooding went on: "The number of vehicle keeper requests that private parking companies make on behalf of their landowner clients is a barometer for how well the private parking system is working.
"We believe that the barometer is reading stormy weather for ministers who have had the responses to the 2015 public consultation on their desks for two years now.
"It is high time that politicians - thinking of their election prospects - and landowners alike woke up to the calls for a better, fairer, properly regulated approach."
A Government spokesman said: "We're committed to reforming unfair parking practices and have already taken steps to tackle rogue private parking operators, including the banning of wheel clamping and towing."