Whitaker, who has been picked for four Olympics, was suspended after his horse Tackeray tested positive for a banned drug, as revealed exclusively in insidethegames on June 28.
 
Traces of the hormone altrenogest were detected in a sample taken from the stallion at La Baule on May 14.

The substance is found in Regumate, a preparation that can legally be given to in-season mares, but not to stallions because it also has a calming effect.
 

Whitaker, 49, has not requested that his B-sample be tested and blames the positive test on a mix-up in feed buckets.

The Yorkshireman claimed that Tackeray was given food out of a bucket normally given to his mares, who do compete using Regumate.

If Whitaker is suspended for longer than six months it means he could be banned from competing in the London 2012 Olympics.

Under the rules of the British Olympic Association (BOA), any competitor who serves a ban longer than six months is ineligible to represent the country again in the Olympics, although they do have the right of appeal.

Whitaker, who along with older brother John has been the back-bone of the British team for decades, challenged the suspension at a preliminary hearing but the suspension was upheld.

Equestrian has been rocked by a series of doping scandals since last year's Olympics, when the events were held in Hong Kong.
 
Six riders, including Ireland's Denis Lynch, received suspensions from competing after their horses tested positive in Hong Kong.
 
It led to inquiry, headed by International Olympic Committee medical adviser Arne Ljungqvist, being set up by the FEI.

Then, just two days before Whitaker's suspension,  five-time Olympic gold medal winner, dressage rider Isabell Werth of Germany, was banned.

Whitaker is among the most popular riders in Britain.
 
He made his debut in international competition at the age of just 16 and at 20 in 1980, he became the youngest winner of the famous Hickstead Derby.
 
Alongside his brother, he was a member of the British show jumping team that won the silver medal at the 1984 Olympics in Los Angeles.
 
He has been selected for three other Olympics but had to withdraw from last year's Games because of an injury to his horse Portofino.
 
In September 1993 he took over from his brother John as the world’s number one show jumping rider.

Whitaker declined to comment on the possible outcome of the case.
 
He said: "There's not much more to be said at this stage."
 

FEI spokesman Malina Gueorguiev said: "We don't know yet whether Michael will appear in person at the tribunal hearing in Lausanne on 11 September."

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June 2009: Exclusive: British star latest top rider to be banned