In his first initiative against indiscipline after taking over as the state BJP chief, Prahlad Joshi took the action against Renukacharya, saying he had been talking "lightly" about some state party leaders.
The expulsion of Renukacharya, close to B S Yeddyurappa, came on a day when he attacked former Chief Minister D V Sadananda Gowda, accusing him of corruption and threatening to expose him more in the coming days.
Gowda had hit back, saying Renukacharya was targeting him as he had acted against him during his chiefministership on certain charges against him.
Renukacharya had made public critical comments against some other leaders, including Deputy Chief Minister K S Eshwarappa, embarrassing the party, which could ill afford any image of indiscipline ahead of the May five Assembly polls.
Renukacharya is expected to join the Karnataka Janatha Party, floated by Yeddyurappa after he broke away from the BJP last year.