"Doubts are being spread about differences between me and Nitish Kumar which is not true ... Some people in a bid to serve their own vested interests are spreading such rumours," Manjhi said at a party function to mark the birth anniversary of socialist leader Karpoori Thakur.
Nitish Kumar and Sharad Yadav were on the dais with him.
Praising Kumar, Manjhi said he showed the "highest level of political ethics" by resigning from the chief minister's post owing moral responsibility for JD(U)'s debacle in the general election.
"Those trying to serve their own vested interest by creating rift between us would not be allowed to succeed. We are one and will remain one," he said.
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Earlier, during the day Yadav concerned over the deepening crisis in JD(U) in the wake of war of words between supporters of Nitish Kumar and Manjhi held a closed door meeting to douse the fire.
Manjhi and state party chief Basistha Narayan Singh were with Yadav in the closed door meeting at the state guest house for more than half an hour.
"Ask Sharad Yadav," he said, when pressed further.
Asked about BJP firing salvos at Kumar and JD(U), Manjhi said "Go and ask Nitish Kumar on this.