Jayant Patil on Saturday said these 18 corporators had defied the party's whip during election.
The Nationalist Congress Party on Saturday expelled all 18 of its newly elected corporators in Maharashtra's Ahmednagar for voting in favour of the BJP during the mayoral poll in the civic body there.
The party's Ahmednagar district chief was also removed from his post.
Last month, 18 NCP corporators voted for the BJP's mayoral candidate Babasaheb Wakale leading to the latter winning despite having just 14 members in the 68-member Ahmednagar Municipal Corporation.
The Shiv Sena had the highest number of 24 corporators in the civic body, elections to which were held on December 10.
State NCP president Jayant Patil on Saturday said these 18 corporators had defied the party's whip during the mayoral election in Ahmednagar.
"They were served show cause notice and were asked to explain their action. However, they have not responded to the notice. Hence, the corporators have been expelled from the party," he said.
He added that Ahmednagar district NCP chief Manikrao Vidhate had been removed from his post as he failed to inform the state party leadership of anti-party activities.
"Vidhate has not even responded to the showcause notice," Mr Patil said.
NCP spokesperson Nawab Malik said, "Its true that due to this decision (expulsion), our party will not have any presence in the civic body. However, no one can hijack the party by defying its whip. We had to take strong action in this regard."
Earlier, NCP chief Sharad Pawar had said that he had taken serious note of the development and had assured strong action.