Detective Chief Inspector Gary Jubelin was booted off the Strike Force Rosann over allegations he used his phone as a recording device without a warrant.
NSW Police confirmed 'an internal investigation is currently underway' by Professional Standards Command into DCI Jubelin.
The March inquest into William's 2014 disappearance is still going to take place despite Detective Chief Inspector Gary Jubelin's absence.
Police confirmed the news in an official statement which read: "The acting state coroner and counsel assisting have been briefed and the William Tyrrell inquest will proceed as planned."
In the interim, Detective Chief Inspector David Laidlaw will be the lead investigator on the team, more than four years after the child's disappearance.