"Congress is like a rainbow, which takes along all the sections of the society with it. It is the only party which can defeat the divisive ideologies of other parties," Kumar, a former IPS officer and plunged into politics three years ago, said after joining the party.
"I will remain as a sincere activist of Congress and will discharge whatever responsibility the party gives," a PCC release said quoting the former Member of Parliament.
Bhagat said, "Ajay Kumar joined the party as he is inspired with the Congress' policies, its principles and leadership."
Kumar had joined Marandi's JVM in 2011 and successfully contested Jamshedpur Lok Sabha bypoll that year. The seat was vacated by BJP leader Arjun Munda after he became the chief minister.
Kumar's quitting the JVM comes close on the heels of a faction of JVM headed by KP Sharma merged with BJP.
This is election year for Jharkhand.