Senior Congress leader from Maharashtra Narayan Rane resigned from the party on 21 September.
He announced the decision a short while back in Sindhudurg in Maharashtra.
The lawmaker from the Kudal constituency has reportedly been negotiating to join the Bharatiya Janata Party (BJP) in the coming days.
He had accused the Congress leadership of not fulfilling the promise of making him the chief minister.
Rane began his political career as a shakha pramukh (local ward chief) in the Shiv Sena, and was the chief minister of the Shiv Sena-BJP government in 1999.