The Fiji Labour Party is demanding an immediate interrogation of the former police commissioner, Colonel Isikia Savua, for his alleged role in plotting the Speight coup.
Colonel Savua is now Fiji's ambassador to the United Nations but is currently present in the country to attend a regional seminar.
Senior Labour MP, Poseci Bune, says police should interrogate him now because they had earlier said they had no money to send an officer to New York.
But the head of the police unit investigating their own officers, Assistant Commissioner Kemueli Bulamainaivalu, has told the Daily Post that their hands are tied because "there is not sufficient evidence" to call Colonel Savua for an interview.
He says they still have to consult the Office of the Director of Public Prosecutions on whether there is evidence of his involvement in the coup.
The commissioner, Andrew Hughes, says the Tuivaga Report on Colonel Savua's alleged involvement has been returned to the President's Office.
Mr Hughes says a criminal file on Colonel Savua collated by police remains open for investigation.