UK Athletics said coach Toni Minichiello, who guided Britain's Jessica Ennis-Hill to heptathlon gold at London 2012, has been provisionally suspended pending an investigation into complaints from female athletes.
UK Athletics, which did not disclose details of the complaints, said it had been forced to make a public announcement after Minichiello was seen coaching athletes in Sheffield, breaching his suspension.
"Following complaints from female athletes, an investigation was commenced concerning Mr Minichiello's behaviour. That investigation is ongoing," UK Athletics said in a statement.
"As a person under investigation, Mr Minichiello's licence was [and remains] suspended pending the conclusion of that investigation.
"UK Athletics is not in a position to say when that will be, but it is pursuing that investigation expeditiously."