Godolphin trainer Mahmood Al Zarooni has been disqualified for eight years by the British Horseracing Authority for doping racehorses in a scandal that has caused serious embarrassment to Dubai ruler Sheikh Mohammed bin Rashid al-Maktoum.

Eleven horses trained by Al Zarooni, 37, in Newmarket in southern England for owner Sheikh Mohammed tested positive for anabolic steroids, including ethylestrenol and stanozolol - the steroid used by disgraced Olympic sprinter Ben Johnson at the 1988 Seoul Olympics.

Al Zarooni, who won the Dubai World Cup - the world's richest horse race for Godolphin in 2012 with Monterosso, as well as two English Classics - the St Leger and 1,000 Guineas, admitted administering prohibited substances to four other horses in his care.

"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," BHA chief executive Paul Bittar said in a statement.

Earlier, the BHA said the 15 horses Emirati Al Zarooni admitted doping, including leading 1,000 Guineas contender Certify, have been banned from racing for six months.

Samples were taken from 45 horses at Godolphin's Moulton Paddocks Stables on April 9. Sheikh Mohammed said on Wednesday that he was "appalled and angered" by the case and announced that the stable would be locked down while doping tests were carried out on all horses under Al Zarooni's care.

Known as the 'sport of kings', Sheikh Mohammed, also Prime Minister of the United Arab Emirates, has become one of the most prominent owners in racing since he established the Godolphin stables in Dubai and England in 1992.

His royal blue silks have won 202 Group One races in 12 different countries and his passion for horses helped transform Dubai into a world power in flat racing, building the sparkling Meydan racecourse which opened in 2010.

Godolphin racing manager Simon Crisford described it as "a terrible day for British racing".

He said: "This is a terrible situation. It's an awful situation that Godolphin has found themselves in. 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."

Al Zarooni, one of two Godolphin trainers based in Newmarket, the headquarters of British flat racing, reiterated that he had made a "catastrophic error".

"First and foremost, I would like to apologise to His Highness Sheikh Mohammed as well as to all those involved with Godolphin and the public who follow British racing," Al Zarooni, training for the Dubai ruler since 2010, said in a statement.

"I accept that it was my responsibility to be aware of the rules regarding 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," he added.

While Al Zarooni breached the rules of British racing, administering drugs to racehorses while they not in training is not outlawed in some countries, notably Australia.

BHA's Bittar said the case served to highlight "inconsistencies across international racing jurisdictions regarding what substances are permitted to be used in training."

"While around the world, horseracing bodies quite rightly adopt a zero tolerance policy to the presence of anabolic steroids when carrying out post-race testing, the approach is not so consistent for horses in training," he said.

"In an age of increasing international travel and competition we will put the subject on the agenda for discussion with our international colleagues," he added.-Reuters