Jitan Ram Manjhi claimed Tejashwi Yadav was helping the National Democratic Alliance in the state.
Former Bihar chief minister Jitan Ram Manjhi on Friday launched a fresh attack on Lalu Yadav's younger son Tejashwi, blaming him for bringing the Grand Alliance on the verge of disintegration.
Mr Manjhi also claimed that the Rashtriya Janata Dal heir apparent was helping the National Democratic Alliance in the state.
A five-party formation headed by the RJD, the Grand Alliance includes Mr Manjhi's Hindustani Awam Morcha (HAM) besides the Congress, former Union minister Upendra Kushwaha's Rashtriya Lok Samta Party and Bollywood set designer-turned-politician Mukesh Sahni's Vikassheel Insan Party.
The coalition has been in turmoil ahead of next month's by-polls to five assembly segments and one Lok Sabha constituency in the state.
"If the Grand Alliance finally disintegrates, it would be blamed on Tejashwi Yadav and no one else. The young leader is, wittingly or unwittingly, helping the NDA, defeating which has been the very motto of the coalition," Mr Manjhi - who was in Araria for a membership drive - said.
"It is not that I made any unreasonable demands. All constituents were in support of my claim over Nathnagar assembly seat. But the RJD ditched us by allotting tickets for four seats, unilaterally, including Nathnagar," he alleged.
Although the RJD is yet to formally announce its candidates for the by-polls, there have been unconfirmed reports that it has distributed tickets for all but Kishanganj assembly and Samastipur Lok Sabha seats, leaving the two for the Congress.
The development has left allies fuming, with Mukesh Sahni announcing that he would enter the fray from Simari Bakhtiyarpur and support Mr Manjhi's candidate in Nathnagar.
He also asserted that "the coalition will survive even if the RJD ceases to be a part of it."
The Congress, which is the RJD's oldest ally, seems to be in a dilemma as its state unit recently moved a proposal that the party should aim at strengthening itself in the long run and go it alone in the by-elections.
The resolution has been forwarded to the party high command for final approval.
Notably, in the Lok Sabha polls, the Congress was the only Grand Alliance constituent to have won a seat in the state. Its Kishanganj MLA Mohd Jawed retained for the party the Lok Sabha seat of the same name.
Mr Manjhi, on his part, urged the Congress to support the HAM candidate in Nathnagar and the VIP nominee in Simari Bakhtiyarpur and promised "whole-hearted support to Congress candidates in the remaining seats".