French racing authority France Galop have suspended jockey Kieren Fallon for six months after testing positive for a prohibited substance.
Fallon has had a turbulent year in 2006
The 41-year-old six-times champion jockey tested positive for a metabolite of a banned substance.
The ban, which is likely to be applied worldwide, is to begin on 7 December.
Fallon is currently banned from riding in Britain after being charged with conspiracy to defraud by the City of London Police.
The ban results from a sample given by the Irishman when he rode Ivan Denisovich in the Prix Jean Prat at Chantilly on 9 July and is likely to be reciprocated internationally.
"We were informed by France Galop this afternoon that Kieren had tested positive for a prohibited substance," said Denis Egan, chief executive of the Irish Turf Club.
"The stewards need to meet first but I would imagine he will be banned from riding in Ireland as well.
Fallon has the right to appeal but both A and B samples tested positive
France Galop spokesman Henri Pouret
"The international jurisdictions sign up to an agreement that if something as straightforward as this happens, we follow their decision.
"As both ourselves and France Galop are signed up to the agreement it seems likely he will be banned from riding in Ireland."
Fallon would be ruled out of the first part of the Classic season.
The quantity of metabolite found was described as "exceedingly low" by expert witness, Dr Michael Lewis, who admitted that there was a possibility that the test result arose solely as a consequence of environmental contact.
Fallon's solicitor Christopher Stewart-Moore said: "Over the course of his long riding career, Kieren Fallon has been tested by authorities all over the world and the results have always been negative.
"In this case, only trace levels were detected and these are considerably lower than generally accepted thresholds for positive results.
"Kieren is dismayed at this turn of events but understands that as it is a strict liability offence, France Galop has no alternative but to impose a suspension."
France Galop spokesman Henri Pouret said "Fallon has the right to appeal but both A and B samples tested positive."
This latest setback throw the Irishman's future in the saddle into further doubt.
Fallon has previously said he will quit racing if he cannot clear his name of race-fixing allegations.
He currently holds the position of stable jockey to the powerful Coolmore operation based at Ballydoyle in Ireland.
A spokesman said the team would "continue to use the best jockey available to them" during the ban.
Fallon has until midnight on Friday to appeal against the suspension.