A preliminary probe into the matter was conducted and a case was filed against Raghubar Das.
A complaint has been registered against outgoing Jharkhand Chief Minister Raghubar Das for allegedly making "objectionable" remarks on Jharkhand Mukti Morcha (JMM) working president Hemant Soren's caste, the police said.
Based on a complaint lodged by Mr Soren on December 19, a preliminary probe into the matter was conducted by Sub-Divisional police officer Arvind Upadhyay and then a first information report was registered at Mihijam police station, Jamtara SP Anshuman Kumar said.
The complaint was registered against the outgoing chief minister under the SC/ST Act on Wednesday, the police said.
Mr Soren had filed the complaint against Mr Das at Dumka Police Station, accusing him of making "objectionable" remarks on his caste during an election meeting in Jamtara, the police said.
"I have filed a complaint with the SC/ST police station in Dumka against the chief minister, who used objectionable words on my caste during a poll meeting at Jamtara's Mihijam on Wednesday," Mr Soren had earlier said.
"His words hurt my feeling and honour. Is it an offence to take birth in a tribal family?" he had said.
BJP Jharkhand unit spokesman Pratul Shahdeo had then claimed that Mr Soren's "absurd allegation" against the chief minister was a tactic after he was deplored for his own remarks.