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 photo 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."