"If anybody goes against the party whip and is found guilty of rebellion, action would be initiated against him," Munde told reporters here.
The Munde senior was humbled on his home turf in Beed district when the nominee fielded by his nephew trounced the candidate fielded by the former deputy Chief Minister.
Deepak Deshmukh, backed by Dhananjay, won the election held last month to the chairmanship of Parli municipal council in Marathwada region.
While Deshmukh polled 26 votes, Jugal Kishore Lohia, a Gopinath Munde loyalist and BJP's official nominee, polled only six. Maharashtra BJP had issued a whip to all party councillors to vote for Lohia.
The 32-member Parli municipal council has 17 BJP members, while the Congress-NCP's combined tally is 14, and one member is independent.
Maharashtra unit BJP chief Sudhir Mungantiwar had yesterday said the disciplinary committee of the party was inquiring into the matter and action will be taken against Dhananjay, if found guilty.