Lalu Prasad will be the alliance's chief ministerial candidate while Paswan's younger brother and LJP's Bihar unit chief Pashupati Kumar Paras is the deputy chief minister aspirant.
Uncertainties had gripped the tie-up over the last three-four days, triggering off speculation that the LJP would join hands with the Congress in case the alliance with the RJD broke down.
"Our alliance (with the RJD) is rock solid and unbreakable. There is no truth in reports that I had talks with the Congress or that I would become a minister at the Centre," Paswan said at a joint press conference with Prasad in Patna.
"The RJD will contest 168 seats and the LJP would be fielding candidates in 75 seats. Lalu Prasad will be the leader of our alliance. He will be projected as the chief ministerial candidate while Pashupati Kumar Paras will the nominee for deputy chief minister," Paswan said.
The LJP chief said he would focus on national politics.
Prasad said the two parties had joined hands after much consideration and added, "The alliance between the two parties will continue even in future."
Prasad, whose party's 15-year rule in Bihar from 1990 to 2005 had been criticised for rise in crime, among other things, sought to assure the people that "the RJD today is not the same RJD."
"The RJD has changed a lot. There were a few people during our rule who brought a bad name to us. If our government comes to power, such elements will not be tolerated."
Prasad's controversial brother-in-law Anirudh Prasad Yadav alias Sadhu Yadav had broken off from the RJD and joined the Congress during the last Lok Sabha elections.
Without naming him, Prasad said, "All such elements have now gathered in the Congress."
