The development reduced RJD's strength in the 75-member Vidhan Parishad to just three.
In a huge setback for the RJD in the election year, five of its MLCs Tuesday resigned from the party, forced a split in its legislature group in the Bihar legislative council, and joined the ruling JD(U) headed by Chief Minister Nitish Kumar.
The development came on a day when former Union minister Raghuvansh Prasad Singh, one of the founding members of the RJD and a staunch supporter of its jailed supremo Lalu Prasad, stepped down as national vice president in protest against the proposed induction of one of his rivals.
The five MLCs SM Qamar Alam, Sanjay Prasad, Radha Charan Seth, Ranvijay Kumar Singh and Dilip Rai met Vidhan Parishad Acting Chairman Awadhesh Narain Singh in his chamber and personally handed over their resignation letters, officials of the Upper House of the bicameral legislature said.
They also requested Singh that they be recognised as a separate group and allowed to merge with the JD(U).
The JD(U)s chief whip in the Upper House Reena Yadav arrived with the party's letter of consent and the Acting Chairman gave his prompt approval.
The development, which blindsided the RJD, reduced the party's strength in the 75-member Vidhan Parishad to just three.
Sources in the ruling NDA were hopeful that Rabri Devi, the wife of RJD supremo Lalu Prasad and a national vice president herself, may lose her position as the leader of the opposition in the House.
Under the rules, the main opposition party must have at least 10 per cent of the total seats in the House for its leader to qualify for the post of the Leader of the Opposition, a Cabinet minister rank position. Meanwhile, Raghuvansh Prasad Singh, who has stood with the party through thick and thin, shot off a letter announcing his resignation from the post expressing strong displeasure over the state of affairs in the RJD.
Mr Singh, who is currently admitted to AIIMS, Patna, undergoing treatment for COVID-19, made it clear that he was not quitting the party but added he was extremely unhappy over the type of people the RJD was planning to induct.
Sources close to the RJD veteran, a former Union minister, confirmed that his displeasure stemmed from reports that Rama Singh, a mafia don-turned-politician to whom he lost his Vaishali Lok Sabha seat in the 2014 Lok Sabha polls, may join the party.
Rama Singh has severed his ties with Ram Vilas Paswans LJP, which had fielded him in the 2014 poll but refused to grant him a ticket five years later.
JD(U) national general secretary and leader in the Lok Sabha Rajiv Ranjan Singh alias Lalan Singh held out an olive branch to Raghuvansh Prasad Singh, saying the RJD has never respected those who have built the organisation.. It is beholden to the interests of just one family. If he wishes to join us, he is welcome.
Raghuvansh Prasad Singh is known to be not on the best of terms with Tejashwi Yadav, Lalu Prasads heir apparent, Tejashwi is the leader of the opposition in the state assembly and the RJD has already declared him the party's chief ministerial candidate for the state elections likely in October-November.
Ever since the RJD was mauled in the Lok Sabha polls last year, the veteran leader has been making a strong pitch for wooing Nitish Kumar back into the Grand Alliance and taking advantage of the frequent differences that have plagued the relations between the JD(U) and the BJP.
His suggestions have, however, invariably been dismissed by Tejashwi Yadav, leaving the rebuffed veteran licking his wounds.
The developments come days ahed of elections to nine seats of the Bihar Vidhan Parishad from the Vidhan Sabha quota where MLAs vote to elect MLCs. The RJD, which has 80 MLAs, has decided to field three candidates.
The party is yet to announce their names and, in the light of the mayhem, it faces the challenge of keeping its flock together.
Meanwhile, the turmoil in the RJD provided its sulking ally, the Hindustani Awam Morcha of former chief minister Jitan Ram Manjhi, with a chance to hit back at the domineering partner.
The RJD is suffering the consequences of ignoring its loyal grassroots level workers to win over those with deep pockets or muscle power. It must mend its ways and start treating its own people besides alliance partners with respect.
"Otherwise a day may come when the RJD will become isolated, with only the members of Lalu Prasads family by its side, HAM spokesman Danish Rizwan said.