The development came on a day the Janta Dal (United) wrote to Yadav, asking him to skip the Rashtriya Janata Dal (RJD) rally in Patna on Sunday and asserted that if he attended it, he would be working "against the party's principles".
It would mean that he has quit the party voluntarily, the JD(U) missive sent to Yadav by its secretary general K C Tyagi, said.
Yadav had earlier said he would be attending the RJD rally and leave for Patna tomorrow.
"We are the founder members of the party. How can Nitish Kumar remove us?," he asked, adding that they were not in a "live-in relationship" with the JD(U) president that he could remove them "as per his whims".
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The Yadav faction has also staked claims over the JD(U)'s poll symbol (arrow) and the offices allotted to the party.
Tyagi had earlier dismissed the claims of the Yadav faction, saying that a rebellion by "two or three persons" could not be described as a split.
The party has removed Yadav as its parliamentary party leader in the Rajya Sabha and also suspended Rajya Sabha member Ali Anwar from the parliamentary party. It has also sacked some office-bearers considered close to Yadav.
Tyagi had said Yadav would be crossing the 'lakshmanrekha' if he attended RJD supremo Lalu Prasad's rally on Sunday, which is likely to see the participation of representatives of several opposition parties.
Shrivastav, however, defended Yadav's decision to attend the rally, saying the JD(U) was a member of the Grand Alliance, comprising the RJD and the Congress, and it remained so for Yadav.
Yadav turned against Kumar after the latter dumped the Grand Alliance and formed a new government in Bihar in alliance with the BJP.