The Garda whistleblower John Wilson claims the force's next Commissioner must be an outsider.
Mr Wilson, who leads the Justice4All campaign, was speaking after the Minister for Justice announced an "open competition" to find the next Commissioner, following the departure of Martin Callinan in March.
John Wilson said he is impressed with Frances Fitzgerald's attempts to reform the criminal justice system to date.
But he said "meaningful reform" of the Gardaí depends on an outside choice.