Parmar resigned from the post after his name did not figure in Congress' first list of candidates for the next month's Assembly polls.
The Congress has fielded Shailesh Parmar from the Danilimbda (SC) seat which falls under Ahmedabad district.
Parmar, a vocal supporter of Dalit rights, said, "to empower Dalit community, it is necessary to capture power. I have joined BJP as Congress is not interested in real empowerment of the community."
Parmar this morning also resigned from the primary membership of Congress and joined the ruling party in the evening. His name figures in the BJP's third list of candidates declared tonight.