The International Olympic Committee said an apology from record-breaking Olympic champion Michael Phelps, who was photographed inhaling from a pipe used for smoking marijuana, was proof enough of his sincerity.

The News of the World ran a picture of Phelps, who won a record eight gold medals at last year's Beijing Olympics, with the glass pipe, saying it was taken at a student party at the University of South Carolina in Columbia last November.

The newspaper did not say Phelps was smoking marijuana but said the glass pipe the swimmer was photographed with was generally used to smoke the drug.

"Michael Phelps is a great Olympic champion. He apologised for his inappropriate behaviour," IOC spokeswoman Emmanuelle Moreau said.

"We have no reason to doubt his sincerity and his commitment to continue to act as a role model."

Phelps, who has won more Olympic gold medals than anyone else after his eight in Beijing and has since signed several endorsement deals worth millions of dollars, apologised saying his behaviour was regrettable.

US officials said the news was disappointing but stressed that smoking marijuana out of competition was not an anti-doping matter.