In a statement released to The Associated Press, the swimmer who won a record eight gold medals at the Beijing Games conceded the authenticity of the exclusive picture published Sunday by the tabloid News of the World.
Phelps said: "I engaged in behavior which was regrettable and demonstrated bad judgment. I'm 23 years old and despite the successes I've had in the pool, I acted in a youthful and inappropriate way, not in a manner people have come to expect from me. For this, I am sorry. I promise my fans and the public it will not happen again."
The nice thing is that -- unlike many steroid abusers -- Phelps has simply admitted that he got caught, even if it was a few months after the fact. That, in my mind, goes a fairly long way towards helping Phelps rehab a clearly damaged image.
Some folks have stated that the media's making too big a deal out of this; yet I don't think it can be overstated just how much Phelps might have cost himself in terms of endorsement money over the past few months.
The field clears a fence during the New Season Handicap Steeplechase during the at Ludlow Racecourse on September 16, 2008 in Ludlow, England.
Emanuele Canonica of Italy helps his caddie in the rescue of a pigeon from the water around the 18th green during the first round of the Portugal Masters at the Oceanico Victoria Golf Course on October 16, 2008 in Vilamoura, Portugal.
A multiexposure image showing Britain's Andy Murray returning to Croatian Marin Cilic during a last sixteen tennis match at the Madrid Masters in Madrid on October 16, 2008. Andy Murray won 7-5, 7-6.
English football fans dressed in armours and tunics play in a friendly match against Belarus fans in Minsk on October 15, 2008 before the start of the Belarus vs. England 2010 FIFA World Cup qualifier of European group 6 match.
Travis Brigley (R) of Hamburg fights with Matt Keith (L) of Ingolstadt during the DEL match between Hamburg Freezers and ERC Ingolstadt at the Color Line Arena on October 14, 2008 in Hamburg, Germany.
Russian Nikolay Davydenko returns a ball to US Robby Ginepri during a second round tennis match at the Masters in Madrid on October 15, 2008.
A golf ball which has been enveloped by the tree over many years is pictured during the pro-am for the Portugal Masters at the Oceanico Victoria Golf Course on October 15, 2008 in Vilamoura, Portugal.
Andy Murray of Great Britain plays football during his training session prior to his thrid round match tomorrow at the Madrid Masters tennis tournament at the Madrid Arena on October 15, 2008 in Madrid, Spain.
Samuel Peter from Nigeria gets a punch from Vitali Klitschko of Ukraine during their WBC heavyweight boxing world championship fight in Berlin, Germany, Saturday, Oct. 11, 2008. Klitschko won the fight after round nine due to technical knock out.
Herbert Knosowski, AP
Japan's Kyoko Hamaguchi (lower) fights with China's Hong Yan (red) during the semi-final of the 72kg class of the Women's Wrestling World Championships in Tokyo on October 13, 2008. Hong defeated Hamaguchi and will face Bulgaria's Stanka Zlateva in the final.