Michael Phelps apologized for "regrettable" behavior and "bad judgment" after a photo of him smoking a marijuana pipe surfaced in British tabloid News of the World.
"I engaged in behavior which was regrettable and demonstrated bad judgment," Phelps said in a statement. "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 photo was taken in November during the 14-time Olympic gold medalist's self-imposed hiatus from the pool following his eight gold-medal haul in Beijing. The tabloid says the picture was snapped at a party at the University of South Carolina.
Marijuana is banned as an "in-competition" substance by the World Anti-Doping Agency, meaning Phelps is unlikely to be hit with any penalties.
"We are disappointed in the behavior recently exhibited by Michael Phelps," the U.S. Olympic Committee said in a statement. "Michael is a role model, and he is well aware of the responsibilities and accountability that come with setting a positive example for others, particularly young people."
This is the second time Phelps' reputation has suffered following a stellar Olympic summer. In 2004, after collecting six gold and two bronze medals at the Athens Olympics, Phelps, then 19, was busted for a DUI and was sentenced to 18 months probation. He also apologized for that incident.