Irish trainer Gerard Butler has been banned from racing for five years over doping offences, the British Horseracing Authority (BHA) announced on Wednesday.
The 47-year-old admitted to seven charges at an inquiry after nine horses in his care tested positive for a banned anabolic steroid.
Butler had claimed that veterinary surgeons had assured him that the substance was legal, but the BHA said he was culpable of "an appalling breach of his duty to look after the interests of the horses in his care".
He had previously admitted to using a steroid called Sungate, which is a treatment for joint pain, but at the hearing he revealed that he had used a substance called Rexogin, which is 10 times more concentrated.
The BHA panel heard that Butler administered Rexogin to four horses using a method of injection reserved for qualified vets.
"Butler's behaviour in administering the injections was consistent with the underhand and covert manner in which he purchased the drug," the BHA panel said.
It added: "Butler's evidence revealed an appalling dereliction of his duty as a licensed trainer.
"By his own admission, Butler kept no clear financial records or any invoice from the purchase of the Rexogin, he did not have the horses properly assessed prior to their treatment and made no recording in his medication records having injected the horses.
"He used junior stable staff to help him who would not question his actions and deceived his senior stable staff and kept from them important information about the treatment given to the horses."
Butler's suspension follows the eight-year ban handed to Godolphin trainer Mahmood Al Zarooni in April after he was found guilty of doping horses in what was the biggest drugs scandal ever to have hit the sport.