Devendra Prasad Yadav-led Samajwadi Janata Dal (Democratic) merged with JD(U), and Samata Party president N K Singh and former RJD minister Baghi Kumar Verma joined the ruling party.
Yadav, who was the RJD MP in the 14th Lok Sabha from Jhanjharpur Lok Sabha seat, merged his SJD (Democratic) with the JD(U) in the presence of Chief Minister Nitish Kumar at a function here.
Speaking on the occasion, he expressed allegiance to Kumar's leadership and said he took the decision to merge his party with the JD(U) to strengthen secular forces in Bihar ahead of the general elections.
The Chief Minister received another shot in his arm as N K Singh and Bagi Kumar Verma joined the ruling party along with hundreds of their supporters.
Singh, a former CBI joint Director, had made the national headlines in late 1970s when he arrested former prime minister Indira Gandhi, and later formed the Samata Party with George Fernandes and Nitish Kumar among several prominent socialist leaders.
He had also unsuccessfully contested against the JD(U) national president Sharad Yadav from Madhepura parliamentary constituency in 1998, 2004 and 2009.