Billy Joe Saunders has been fined £100,000 and given a severe reprimand about his future conduct after video footage emerged of him appearing to offer a woman drugs.
Saunders' actions were filmed from his car and seemingly show him offering £150 worth of drugs to the woman to perform a sex act as well as asking her to punch a passer-by, which she does, before he drives off.
The WBO middleweight champion was last week hit with a misconduct charge by the British Boxing Board of Control, which found Saunders guilty of bringing the sport into disrepute at a hearing on Tuesday.
A BBBofC statement said: "Billy Joe Saunders appeared before the stewards of the British Boxing Board of Control today under a misconduct charge following his recent behaviour shown on social media.
"The stewards have found Mr Saunders guilty of bringing the sport of boxing into disrepute and have fined him the sum of £100,000 and issued a severe reprimand as to his future conduct.
"All monies will go to the BBBofC charity to assist ex-boxers and ex-licence holders who have fallen on hard times."
No drugs could be seen in the clip and the 29-year-old Saunders, who is due to defend his title against Demetrius Andrade in Boston on October 20, described the incident as an ill-judged joke.
He wrote on Twitter last week: "(I) apologise to everybody who's took offence, totally in the wrong, can't do anything but be sorry. 'Banter when wrong'. Apologies once again."
A statement released by Nottinghamshire Police described the footage as "sickening", and an investigation is to be launched into the "number of offences" seen.
The incident is the latest to undermine Saunders' reputation.
Last December he produced a career-best performance that was considered among the finest by any Briton fighting overseas, to outpoint David Lemieux in Canada.
But he was then criticised for withdrawing from another fight with Martin Murray through injury and has since been inactive.
In Belfast last month he was also chased out of a restaurant, having allegedly thrown chicken at WBC heavyweight champion Deontay Wilder, who is scheduled to fight his friend Tyson Fury.