"I find the PM's silence baffling. He has been hailed as a great communicator; he has been quick to take to microphone, the TV camera and Twitter to express his views on all sorts of things. But on all key issues facing our nation, there has been no communication from the PM," Tharoor said.
"Even in this incident (Dalit scholar's suicide), the PM spoke almost after a week. (Congress vice president) Rahul Gandhi has been there days ago and the PM has only spoken yesterday," he said.
Rohith Vemula, who committed suicide on Sunday night, was among five research scholars who were suspended by Hyderabad Central University (HCU) in August last year and also one of the accused in the case of assault on a student leader. They were also kept out of the hostel.
Tharoor also said that India was still very conscious of caste and there existed a perception of discrimination against Dalits.
"After the tragedy, I got many letters and emails from Dalit students talking about what they say is a pervasive discrimination against Dalit students, scholars and researchers.