Professor David Nutt received a call from a displeased British Home Secretary after his views were published in the Journal of Psychopharmacology, and now the British Horse Society has waded into the debate.
Nutt, who is chairman of Britain's Advisory Council on the Misuse of Drugs (ACMD), penned an article entitled "Equasy - An overlooked addiction with implications for the current debate on drug".
In it, he wrote: "The point was to get people to understand that drug harm can be equal to harms in other parts of life."
The professor, using the term Equasy to refer to equine addiction syndrome, continued: "There is not much difference between horse-riding and ecstasy. This attitude raises the critical question of why society tolerates - indeed encourages - certain forms of potentially harmful behaviour but not others such as drug use."
The British Horse Society (BHS), in responding to the comments, pointed to the health benefits of riding, and the contributions that it makes to the overall health of the nation.
It described a comparison between riding and the use of the drugs as inaccurate and "unhelpful for those who wish to pursue riding as part of a healthy lifestyle".
"How anyone can suggest that the clear dangers of drug abuse equate in the slightest degree to horse riding is beyond me," said Mark Weston, the BHS director of access, safety and welfare. "The health benefits of horse riding are well known."
Horse riding is known to control weight, build healthy bones and muscles, and reduce the risk of heart disease, diabetes, cancer and premature death through promoting an active lifestyle, he said. It is a beneficial activity for all adults, particularly the very young and the very old.
Riding and caring for horses is known to improve self-esteem, reduce stress, anxiety and depression, and improve psychological wellbeing without the use of drugs.
Heather Holmes, the society's senior executive responsible for access issues, said: "I understand how comparisons can be beneficial to highlight a point in a study. However, these must be factually accurate and well researched to be used fairly. I am relieved and thankful to see that the Government have distanced themselves from Professor Nutt's comments."
Holmes was referring to earlier comments by the British Home Secretary Jacqui Smith, who voiced her concerns over Professor Nutt's views during question time in the House of Commons.
"I made clear to Professor Nutt that I felt his comments went beyond the scientific advice that I expect of him as the chair of the Advisory Council on the Misuse of Drugs (ACMD)."
She said the professor had apologised to her.
Smith continued: "I'm sure most people would simply not accept the link that he makes up in his article between horse riding and illegal drug taking.
"For me that makes light of a serious problem, trivialises the dangers of drugs, shows insensitivity to the families of victims of ecstasy and sends the wrong message to young people about the dangers of drugs."
BHS chief executive Graham Cory provided his views to the professor in a letter the society publicly released.
He outlined a long list of health benefits from horse-riding and then continued: "Which were the corresponding benefits of ecstasy you had in mind when, after scholarly consideration, you decided upon the equivalence of the two?
"Whereas the autodidact might indeed syllogise, 'People sometimes fall off horses; falling off horses and taking ecstasy can be dangerous; therefore riding horses is as dangerous as taking ecstasy', I am sure the academic's reasoning will be far more enlightening."