LJP president Chirag Paswan said on Saturday that it was the BJP's prerogative to announce a candidate for the Bihar Rajya Sabha election.
The seat had fallen vacant following the death of Chirag Paswan's father and Lok Janshakti Party founder, Ram Vilas Paswan. The BJP has nominated former Bihar deputy chief minister, Sushil Kumar Modi, for the seat.
Sushil Modi is likely to win uncontested unless the opposition Grand Alliance fields a candidate to challenge him. In that event, the polling will take place on December 14.
A union minister, Ram Vilas Paswan had got elected from the seat last year after it fell vacant following his cabinet colleague Ravi Shankar Prasad's election to the Lok Sabha from Patna Sahib
"The seat belonged to the BJP and it is for the party to decide which candidate from which party to field in the by-election," the 37-year-old leader told reporters.
At an event, Chirag Paswan asked the party rank and file to gear up for the next assembly polls which could take place "any time".
Responding to questions, Mr Paswan maintained that he saw "fresh elections taking place any time in Bihar, given the way the new government is functioning".
In a written message to party workers, Mr Paswan defended his decision to go solo in the assembly polls, saying, "We had to make a choice between accepting the NDA's offer of only 15 seats despite being a party with six members in the Lok Sabha and one in the Rajya Sabha, or engage in a friendly fight to preserve our honour".
The LJP chief, under whose stewardship the party fought more than half of the seats in the 243-strong assembly but won only one, tried to cheer up his supporters and asked them to focus on the bright side.
"We could win only two seats in the previous assembly elections even though we had contested as part of the NDA. This time, we were alone, without an army of star campaigners to canvass in our favour. But we secured 28 lakh votes and now our party is being talked about across the state," Mr Paswan said.