Police in Fife said the “reckless and selfish” motorist had provided the highest alcohol reading of the entire Christmas and New Year crackdown.
The incident happened on January 2 in Kirkcaldy when officers pulled over the car because of a “minor deficiency”.
The learner passed a breath test but the supervisor – a 30-year man – had 125 milligrams of alcohol in 100 millilitres of breath.
Chief Superintendent Alistair McKeen said: “They were not only putting the driver at risk but putting the public at risk because the learner driver was effectively flying solo and would have been as well driving with no-one in the car.
“The fact that we had someone here who was four times over the limit indicates that they don’t have the faculty to supervise someone the way they should have been.
“The driver could have found himself in some difficult situation with the road conditions.
“In my view it was reckless and selfish of him to agree to supervise.
“It is certainly astonishing to get anyone with that amount of alcohol in their bloodstream whether they are supervising or driving themselves.”
He added: “The main thing is here is that bear in mind that this happened during the hours of darkness and road conditions were treacherous across Fife. Any learner driver would have found it difficult to drive.
Chief Superintendent McKeen added that supervising a learner driver carries the same penalties under drink-drive laws as though they themselves were driving.
He said: “The person in charge of the vehicle is deemed to be the passenger. The penalties for someone in charge of a vehicle in that condition are identical to someone who was actually driving. He will lose his license.
“Just because you’re not driving doesn’t stop you from being responsible.”
But the police superintendent added that the blame shouldn’t be completely placed on the supervisor and that learner drivers should be aware of who is capable of taking them out.
He added: “Learner drivers should be aware that they are required to be supervised by a proficient driver who has a full licence and who is completely sober.”