Godolphin racing manager Simon Crisford spoke of "a terrible day for British racing" after trainer Mahmood Al Zarooni was disqualified for eight years after admitting administering anabolic steroids to horses in his care.
Al Zarooni said he had made a "catastrophic error" in using the banned drugs on a number of runners in his yard, including former Qipco 1000 Guineas favourite Certify.
Al Zarooni was called before the British Horseracing Authority disciplinary panel at a hastily-arranged hearing on Thursday afternoon after 11 horses returned positive samples for ethylestranol and stanozolol following a random testing at his Newmarket yard earlier this month.
Further admissions were made by Al Zarooni to the BHA this week surrounding four other horses that had not been tested.
The case, widely regarded to be the most serious doping scandal in recent British racing history, had already caused Godolphin principal Sheikh Mohammed to lock down Al Zarooni's stables, saying he was "appalled and angered" by events.
Al Zarooni, 37, was officially charged with rule breaches related to prohibited substances, duty to keep medication records and conduct prejudicial to racing.
Earlier in the day, the fifteen horses were banned from running for six months from 9 April.
Crisford said: "This is a terrible situation. It's an awful situation that Godolphin has found themselves in.
"Mr Al Zarooni acted with awful recklessness and caused tremendous damage, not only to Godolphin and British racing.
"I think it will take a very long time for Godolphin to regain the trust of the British public.
"We're shocked and completely outraged by the actions he has taken."
Crisford also confirmed Al Zarooni had mentioned the names of three other people - two foremen and a veterinary assistant - who were "involved".
However, he said the assistant had not broken any rules because he was unaware what substance he was administering.
Crisford said Al Zarooni had previously administered steroids in Dubai, where it is not prohibited.
Referring to the contravention of British rules, he said: "This is an isolated incident at the hands of a reckless person who has shown no respect for horse racing in this country."
Asked about Sheikh Mohammed's views on the incident in Britain, Crisford said: "He will want, first and foremost, to see this put behind us. He will want to make sure this mistake never happens again."
Al Zarooni issued a statement that read: "I would like to apologise to Sheikh Mohammed, as well as to all those involved with Godolphin and the public who follow British racing.
"I accept that it was my responsibility to be aware of the rules regarding the use of prohibited substances in Britain.
"I can only apologise and repeat what I said in my statement earlier in the week, I have made a catastrophic error."
BHA chief executive Paul Bittar said he believed the punishment would reassure the public and the racing industry that the use of performance-enhancing drugs would not be tolerated.
In a statement, he said: "The relevant rules in this case are explicit in that the use of anabolic steroids in horses in the care of a licensed trainer is prohibited and that strict liability for everything administered to horses while they are in training lies with the trainer.
"We believe that the eight-year disqualification issued to Mahmood Al Zarooni by the disciplinary panel, together with the six-month racing restriction placed on the horses in question by the BHA, will serve to reassure the public, and the sport's participants, that use of performance-enhancing substances in British racing will not be tolerated and that the sport has in place a robust and effective anti-doping and medication control programme."
Bittar added: "This rapid resolution would also not have been possible without the full cooperation of Godolphin and Sheikh Mohammed.
"The relevant rules in this case are explicit in that the use of anabolic steroids in horses in the care of a licensed trainer is prohibited and that strict liability for everything administered to horses while they are in training lies with the trainer."
The BHA's investigation established that the substances in question were administered on the instruction of Al Zarooni.
He said the full details of how the substances were administered would be published later.