A horse belonging to and ridden by Sheikh Mohammed has tested positive to banned substances during competition.

The horse — Tahhan — was tested last week during routine post-competition checks by Sheikh Mohammed’s personal staff in the United Arab Emirates (UAE).

Two banned substances — Guanabenz and 16b Hydroxy-Stanozol — were found by his team after an international and national endurance competitions in the UAE.

A statement issued last night on behalf HH Sheikh Mohammed Bin Rashid Bin Rashid Al Maktoum said the ruler of Dubai had offered the “highest level of cooperation to the International Equestrian Federation (FEI)”.

The statement continued: “His highness immediately requested his representative contact the FEI and advise them of this information in order that they may correct the placings as Sheikh Mohammed considers his results null and void.”

While Sheikh Mohammed stressed he was “completely unaware and utterly condemning of the administration of these substances”, the news is likely to have caused embarrassment in the royal household.

His second wife, Princess Haya, is president of the FEI, an organisation which has been very publicly been trying to clamp down on doping in horse sport.

Late last night, following the release of a statement by her husband, Princess Haya issued her own line.

“Princess Haya has recommended that the role of president in this instance, and all matters relating to this subject, be deferred to Mr Chris Hodson, second vice-president of the FEI, who is himself a lawyer.

“Additionally, although endurance is not an Olympic discipline, but in view of her position as a member of the International Olympic Committee (IOC), Princess Haya immediately notified the IOC Ethics Commission of her decision to defer the presidency of the FEI in this matter.”

Sheikh Mohammed has started his own internal investigation into the dopings, and imposed a competition ban on himself — which has not yet been requested by the FEI.

He has also volunteered his acceptance that he is legally the “person responsible” for the horses.