Who had first given the idea of a Constituent Assembly to frame a Constitution of India?

M N Roy Rajendra Prasad Mahatma Gandhi Jawahar Lal Nehru

M N Roy

The idea for a Constituent Assembly was proposed in Dec 1934 by M. N. Roy, a pioneer of the Communist movement in India and an advocate of radical democracy. It became an official demand of the Indian National Congress in 1935.