"Only a CBI investigation can expose the Saradha scam," Mitra told reporters at Dubrajpur in Birbhum district.
Earlier, Mitra took part in a programme organised by the Loba Krishi Jami Raksha Committee, along with PDS leader Samir Putatundu and a number of district Congress leaders.
"I have heard about the agitation of the people of Loba from my friend Samir. I have come here to support this agitation actively. What surprises me that even after the Singur and Nandigram agitations the people of Loba are still fighting to get their rights," Mitra said.