The horse tested positive at the the Rhineland Championships in Langenfeld in June 2012 after, according to Werth, having drunk contaminated water due to a problem with her automatic watering system.

The Federation found this explanation to be "extremely unlikely" and, following an "extensive investigation", believe instead that the horse ingested cimetidine by putting his head through the bars of his neighbour's stable - who was being treated with the substance.

Although accepting that it was an accident, the German Federation stated that "this constitutes a breach of duty of care in the organisation of their stable operation for which the rider is responsible."

Consequently, the 44-year-old Werth has been banned from national and international competitions for six months and handed an additional pay a fine of €2,000 ($2,600/£1,700) as well as to cover legal costs. 

The substance, used to treat stomach ulcers, is not illegal at international level but is banned by the German Federation.

Isabell Werth, pictured competing at the 2011 European Championships, has been suspended from competition for six months



Werth has enjoyed a successful career which has included team gold medals at the Barcelona 1992, Sydney 2000 and Beijing 2008 Games, as well as both the team and individual titles at Atlanta 1996.

But this is the second occasion on which she has been banned for a failed test on one of her horses.

In 2009 she was suspended by the International Equestrian Federation (FEI) when her horse Whisper tested positive for fluphenazine.

This follows a spate of other failed tests in the sport, particularly in endurance racing involving teams from the Middle East.

Werth may appeal the verdict. 

"First we will wait for the substantiation of the first chamber, and then we'll see," she told the German website St Georg.

"After we've read the substantiation we will appeal and then we'll go to the court of arbitration."