An Irish Olympic sailor received a warning from the IOC on Tuesday for betting on a rival to win, escaping a suspension because of the "special circumstances" in the case.

The International Olympic Committee executive board ruled that Peter O'Leary violated betting rules when he placed two bets on Britain to win the men's Star event at the 2008 Beijing Games.

O'Leary allegedly placed bets worth 300 euros ($A378.81) with an Irish bookmaker at odds of 12-1, collecting 3,600 euros ($A4,545.74) when Britain took the gold.

IOC rules bar athletes from betting on Olympic events.

The case only came to light during the London Olympics when someone informed the Olympic Council of Ireland by email of the bets.

After an investigation by its ethics commission, the IOC said there was no evidence of match-fixing and O'Leary had not been fully aware of the betting rules at the time.

O'Leary could have faced a suspension, but the IOC said a warning was sufficient because his activity had "no impact" on the result.

"No proof of any match-fixing of the competition was found," IOC spokesman Mark Adams said. "While the executive board views any breach of its betting rules as a serious matter, it considered the special circumstances of this case when taking this decision."

O'Leary and teammate Stephen Milne did not qualify for the medal race of the Star competition in Beijing, which was won by Britain's Iain Percy and Andrew Simpson.

O'Leary finished 10th in the Star at the London Games with David Burrows.

The IOC has led efforts in recent years to bring sports federations, law enforcement agencies, governments and the legal gambling operators together to coordinate and fund the fight against betting corruption.

AP