Under proposals being considered by ministers, the committees are to be replaced by three individual monitors.
Speaking after concerns were raised by the Howard League for Penal Reform, Ms Boyack said: “I recently met members of Edinburgh’s visiting committee and they expressed strong reservations about the path the Scottish Government is following. These volunteers have developed a strong link with the prison and have a rapport with the inmates, who trust them to raise issues of concern.
“Replacing these dedicated volunteers with just three national monitors would sever this link and make it virtually impossible for individual complaints to be dealt with. This has clear implications on our duty to ensure that inmate accommodation is safe.
“I am also concerned about the independence of the monitors given that they are likely to be drawn from a pool of ex-governors and civil servants.”