The 57-year-old man, who was not named pending trial, was also charged with illegally practising medicine as an alternative "energy therapist" without a licence, the head prosecutor in the northeastern town of Verdun, Yves Le Clair, told AFP.
Police were alerted to the suspect when a Belgian woman and a Frenchwoman complained to authorities that they were touched sexually by the man during sessions in his clinic in Dun-sur-Meuse, near Verdun.
Le Clair said eight alleged victims had been identified so far, all women aged between 40 and 60 who were stricken with illnesses not able to be cured by conventional doctors.
The suspect had been forced to resign from the Belgian police service after being convicted in 2006 of breaking police confidentiality.
He was put under investigation in 2007 by the Belgian police after starting a website offering to cure children of certain maladies.
He was detained Friday pending trial on charges of sexually assaulting and defrauding vulnerable people and illegally practising medicine.