The Australian jockey Damien Oliver, who will ride Americain in the Melbourne Cup later on Tuesday, has admitted to placing an illegal bet on a rival horse and could face a lengthy ban.
The allegations have cast a cloud over Australia's richest horse race with pundits administrators criticised for allowing the jockey, a former Melbourne Cup winner, to ride.
Oliver, who won the 2002 Melbourne Cup on Media Puzzle, has admitted to racing stewards that he had placed a $10,000 bet on Miss Octopussy in a local race two years ago in which he rode another horse, according to Fairfax media reports.
Stewards revealed last month that they had been investigating Oliver over the illegal bet.
The allegations against Oliver are part of a wider investigation into corruption in horse racing in the state of Victoria.