In the letter to the PM written yesterday, Dudi said that state government was not dealing with the case with a humanitarian point of view.
Dudi today also alleged that efforts were on to shield one of the accused who is linked to RSS and demanded a CBI probe into the case.
"Bikaner police is trying to protect the accused and the investigation is not being impartial under pressure because one of the accused, who is the owner of an educational institute, is from RSS," Dudi told reporters here.
The minor girl, who was persuing BSTC (a teacher's training course) in a private educational institute in Bikaner, was found dead in a water tank of the institution on March 30.
On the intervening night of March 28-29, she was found in the room of the physical trainer and instructor, Vijendra Singh, by the hostel warden where she was allegedly raped.
The physical instructor, the hostel warden and principal were apprehended in connection with the incident.