The move came after reports that BSP had declared Nishad as its candidate from the Shahjahanpur constituency for the Lok Sabha polls due in 2014.
The party found Nishad guilty of "hobnobbing with the BSP" which came under ambit of "indiscipline", said Ram Krishna Dwivedi, chairman of party's disciplinary committee.
He said party has send a letter to Nishad, telling him that he was expelled for "hiding his real intentions" by "remaining in contact" with BSP despite being a Congress member.
On BSP's claims that Nishad had resigned from Congress yesterday to join its party, Dwivedi said the party did not receive any resignation letter from the leader.