Renowned jockey Frankie Dettori will learn his fate for failing a drugs test when French racing's ruling body issues its verdict on Tuesday (Wednesday AEDT).

The England-based Italian failed a test after riding in the Prix de l'Arc de Triomphe trials at Longchamp on September 16.

Through his lawyer, Christopher Stewart-Moore, the jockey admitted to testing positive for a non-performance enhancing product.

Both France Galop and Dettori's legal team have steadfastly refused to identify the substance.

British media have reported it was a recreational drug which could mean a six-month worldwide ban.

However, a more run-of-the-mill product, such as treatment for a common cold, could result in a reprimand.

The feeling from racing insiders is that with the dossier having been handed on to the stewards by the medical commission is that he is facing a highly-damaging ban of several months.

It will be especially damaging for the exuberant Dettori because he recently had his lucrative contract with the Dubai-based Godolphin operation terminated after 18 years of success for both parties.

The final straw for both sides came not with the drug test failure but when Dettori accepted the ride on Epsom and Irish Derby champion Camelot for Godolphin's bitter rivals Coolmore Stud in October's Arc.

It brought to a head the deterioration in the relationship between Dettori and Sheikh Mohammed's Godolphin.

Ironically it was a previous drugs offence that enabled Dettori to sign for Godolphin after a high-profile contract in Hong Kong fell through when he received a police caution in 1993 for possessing a small amount of cocaine.

While a six month ban would mean Dettori would be back in the saddle by June 4, he would have missed all the main European Guineas classics as well as the blue riband Epsom Derby and the Oaks.

Hopes of being signed up by Coolmore as stable jockey, where present number one Joseph O'Brien, son of their trainer Aidan O'Brien, is fighting a losing battle with his weight, would also fall by the wayside.

A well-placed source told AFP Dettori would seek to have any ban backdated to the last time he rode which was aboard Cavalryman in the Melbourne Cup on November 6.

However, France Galop has never before backdated bans so Dettori faces a tough task to persuade them to break that habit.