Tens of thousands of people could be paying fraudsters to sit their driving test for them, the BBC has learned.
Drivers who have not passed the test are more likely to crash
The Driving Standards Agency (DSA) says impostors charge up to £500 and can have taken more than 200 tests each.
The scam works when the fraudsters pass themselves off as the person in the photo on the provisional licence that candidates must bring to their test.
The DSA described the problem, the scale of which has only recently become clear, as serious.
Difficult to spot
The head of the DSA's fraud team, Andy Rice, said: "It is quite common for them to do over 100, sometimes over 200 tests, before we're in a position to arrest them. It potentially could be into the tens of thousands."
Many of the fraudsters have sat tests at different driving centres around the country.
If they pass the test, the person paying them is granted a full licence - despite having never sat a practical road examination.
Ashley Bateman, a driving examiner in Nottingham, explained that it could be difficult to spot those trying to cheat the system.
"If their face looked the same shape and they had the same colour eyes and things like that, there is a chance then that it would be difficult for the examiner to identify there's a problem," he said.
The AA's head of road safety, Andrew Howard, said he was shocked at the size of the problem and he believed it could be related to the increasing difficulty of the driving test.
"As the tests get harder to make the roads safer, more and more people will do whatever it takes to get around the hard exam," he said.
He also pointed out that drivers who had not passed a test were up to nine times more likely to have an accident, and it was more likely to be a serious one.
Shadow Transport Secretary Chris Grayling said: "This is yet more evidence that there are hundreds of thousands, if not millions, of rogue drivers on our roads without tax or insurance and now, it appears, often without a legal driving licence.
"This is a huge road safety challenge and we clearly need urgent action to tackle the problem."
There are already cases of alleged falsehoods reaching the courts.
On Monday, two men from Oldham, Greater Manchester, were convicted of obtaining driving licences by deception.
Shazad Akhtar, 34, of Bolton Street, was sentenced to 200 hours of community service and ordered to pay £500 costs after pleading guilty to 22 counts of obtaining and attempting to obtain driving licences by deception.
Mushtaq Ahmed, 37, of Roundthorn Road, was fined £200 for obtaining a driving licence by deception.
The DSA, which gathers evidence before handing it on to police, has run 1,200 investigations into the activity so far.
The fear is that the figures are the tip of the iceberg and that there are many more untested and potentially lethal drivers on the roads.