The number of parking tickets handed to drivers has risen by almost one million in just 12 months, according to a motoring research charity.
RAC Foundation analysis of government data shows 5.65 million vehicle keeper records were obtained from the Driver and Vehicle Licensing Agency (DVLA) by parking management firms in the last financial year.
This is a 20% increase on the total of 4.71 million during 2016/17.
A decade ago, in 2007/08, fewer than half a million records were released.
Parking companies use the information to chase vehicle owners for alleged infringements in private car parks, sending penalty charges of up to £100.
The latest figures suggest a penalty notice is being issued every six seconds.
RAC Foundation director Steve Gooding said: "Each year we are not only astonished by the numbers involved, but also by the fact that those numbers keep rocketing up.
"The true volume of tickets being issued might actually be significantly higher still as some firms will simply slap a demand on to a windscreen for the driver to find when they return to their vehicle.
"What's going wrong? Are Britain's motorists really flouting the rules on such an industrial scale?"
The Government has committed to back a Private Member's Bill which would lead to the introduction of a code of conduct for private car park operators.
Tory former minister Sir Greg Knight's Parking (Code of Practice) Bill had its second reading in the House of Commons in February.
Mr Gooding said: "We strongly support Sir Greg Knight in his initiative to get some regulation in place through a Private Member's Bill that will establish much-needed independent scrutiny of what's going on in the private parking world.
"Only then can we be reassured that the cards aren't stacked against the motorist."
ParkingEye Ltd obtained the largest amount of data in 2017/18 at 1.8 million records.
The DVLA charges private firms £2.50 per record, meaning the agency could have collected £14.1 million during this period.
A DVLA spokeswoman said the charges were set to recover the cost of providing the information, and the agency did not make any money from the process.
Communities minister Rishi Sunak said: "We've promised we'd put a stop to cowboy operators ripping off drivers and, through the Parking Bill, we'll do just that.
"Whilst many operators abide by the rules, dodgy firms have been pulling a fast one at motorists' expense for too long.
"We'll halt aggressive letters, small signs and unfair fines. If they don't toe the line, we'll put them out of business."