Paris - Italian jockey Frankie Dettori has been banned from riding in French races for six months after a positive dope test at Longchamp, the French racing authority said on Wednesday.
Dettori, 41, tested positive for the unidentified substance on September 16.
"France Galop stewards decided to ban jockey Frankie Dettori from riding in public races from December 19, 2012 to May 19, 2013," the French authority said in a statement.
"They also asked the foreign racing authorities to extend the ban to the races they rule."
Dettori was suspended for six months in 2006 after failing a drugs test.
The British-based jockey will also have to undergo a further test from April 20 next year before he is cleared to resume riding.
"Samples will be taken during this medical in order to test him for prohibited substances again," the statement said.
Dettori, one of the biggest names in flat racing, won all seven races in one afternoon at Ascot in 1996, costing bookmakers millions of pounds in payouts.
He announced in October that he was ending his 18-year stint as the retained jockey for the Godolphin stable of Sheikh Mohammed, for whom he has ridden 110 Group One winners around the world since 1994.
Dettori's solicitor Christopher Stewart-Moore said in a statement his client fully accepted the decision.
"He also accepts that he has let down the sport he loves and all those associated with it, as well as the wider public. But most of all - and this is his greatest regret - he has let down his wife and children," Stewart-Moore said.
"Racing has been good to Frankie, and he knows that his privileged position brings with it responsibility. For this reason, he is determined to re-build his reputation when he returns to the saddle in six months' time."