Convicted pedophile Dennis Ferguson has been ordered to leave an inner Sydney swimming pool, packed with children attending an open day.

A member of the public contacted the pool's management after spotting Mr Ferguson going into the changeroom of the complex on Sunday, Network Seven reported.

Hundreds of people, including many children, were attending an open day at the pool at the time.

Police were contacted and officers approached Mr Ferguson, who completed a 14-year sentence for sexually assaulting three children aged six, seven and eight in a Brisbane motel in 1987.

Network Seven said there was no suggestion by police or any member of the public that Mr Ferguson was doing anything wrong when he was asked to leave.