The DVLA has sold the details of more than 1.7 million drivers to private parking firms in three months.
And by charging £2.50 a time, the Driver and Vehicle Licensing Agency stands to raise at least £4.35m for the 1.74m records it passed on between April and June.
Some 19,000 registered owners’ details were sold each day during the period. The firms use the information to chase up unpaid parking tickets.
ParkingEye Ltd obtained the largest amount of information at 570,000 records, Smart Parking received 125,000 and Euro Car Parks 118,000.
The RAC Foundation said there had been a 64% surge in the number of details being handed over to parking firms when compared with the same period last year.
If a similar amount of information is sold by the DVLA over the remaining three quarters of this year, the annual total would be seven million details, up from 4.7 million in 2016/17.
To access the data, parking firms must be members of a trade association, either the British Parking Association (BPA) or the International Parking Community (IPC).
The information is used to chase vehicle owners who have been ticketed in privately run car parks – at hospitals, pubs, hotels, supermarkets and shopping centres.
Conservative MP Sir Greg Knight tabled a private members’ bill in the last week of Parliament to introduce a single nationwide legally-binding code of conduct for car parking firms.
RAC Foundation director Steve Gooding said: “Self-regulation of the private parking sector has not worked – even many of the big companies acknowledge that – and we are delighted [the bill] that will create a single, binding code of conduct, something we have campaigned for over several years.
“Private parking has turned into an industry worth hundreds of millions of pounds with many firms relying on enforcement as their only way of making money.
“No wonder the DVLA is now being inundated annually with many millions of requests for vehicle keeper data so drivers can be sent penalty tickets on often dubious grounds.”
The DVLA insists it does not make money out of the practice and that the fee charged merely covers admin costs.
A DVLA spokeswoman said: “We take our responsibility to protect information extremely seriously and we have robust safeguards in place to ensure data is used correctly. Our data release charges are set to recover the cost of providing the information.”