A statement on the Godolphin website read: "Following an inspection of Zarooni's stable by officials from the British Horseracing Authority, traces of prohibited substances were discovered in a number of the horses tested, including Certify.
"The BHA has advised that, as a result, the filly will not be allowed to take part in the Qipco 1000 Guineas at Newmarket next month."
Godolphin trainer Al Zarooni based in Newmarket said on www.godolphin.com: "I deeply regret what has happened. I have made a catastrophic error.
"Because the horses involved were not racing at the time, I did not realise that what I was doing was in breach of the rules of racing. I can only apologise for the damage this will cause to Godolphin and to racing generally."