"After sharing power with the ruling JD-U for over seven-and-half years, BJP will sit in opposition," Bihar BJP president Mangal Pandey said.
BJP legislators have elected Nand Kishore Yadav as leader of opposition in the state assembly and Sushil Kumar Modi as leader of opposition in the legislative council.
The party has also issued a whip to its 91 legislators to vote against the JD-U government during the vote of confidence here.
Soon after the JD-U ended its 17-year-old alliance with the Bharatiya Janata Party (BJP) Sunday, Nitish Kumar said he would seek a vote of confidence at a special session of the state assembly June 19.
Nitish Kumar called off the alliance with the BJP and his colleague Sharad Yadav quit as the convenor of the BJP-led National Democratic Alliance (NDA) following differences with the BJP over the growing clout of Gujarat Chief Minister Narendra Modi.
Party legislators held a meeting at the official residence of former deputy chief minister Sushil Kumar Modi where they elected Yadav, who is former road construction minister, as leader of opposition in the state assembly and Modi as leader of opposition in the legislative council.
However, some senior BJP leaders, including two former ministers Prem Kumar and Chandra Mohan Rai, have expressed their displeasure at the way Yadav was elected leader of opposition.
Kumar and Rai, who were peeved, did not attended the BJP legislature party meeting here.
Nitish Kumar is confident of proving his majority in the assembly after dumping the BJP as an ally. Four of the six Independent legislators announced their support to Nitish Kumar and the sole LJP legislator, Zakir Hussain Khan, has also announced his support to the government.
"We have the magic number of 123 including 118 JD-U legislators, four independents and one LJP and one CPI legislator," JD-U spokesperson Neeraj Kumar has said.
According to JD-U leaders, the Congress with four legislators is likely to abstain during the vote of confidence.