Kumar was a medico before joining Indian Police Services and served as SP in Jamshedpur from 1994-1996.
After resigning from the IPS, he served for a brief stint in corporate sector before joining Babulal Marandi's JVM(P) and became an MP in 2011, defeating Congress's Banna Gupta.
He had joined Congress last month in Ranchi vowing to fight the "communal forces" during the coming assembly election.
Kumar's claim to fame before joining politics has been the work done by him to restore law and order during his stint as Jamshedpur SP.
Kumar hails from Karnataka and there was speculation that he could be nominated for Rajya Sabha from his native state in future.
"Ajoy Kumar, ex-MP of Jharkhand has been added to the list of existing spokespersons," AICC general secretary and Communication Department Chairman Ajay Maken said.