"I am fighting against injustice done to me," Yadav, who was given BJP ticket, told reporters on his first visit to the BJP headquarters here.
Yadav was denied ticket from the seat by the RJD which went to the Lalu's eldest daughter Misa Bharti. This led Yadav to cross over to the BJP.
"This is a fight for development and a strong government across the country and 'bhai' Narendra Modi is the choice of all people," he said.
Meanwhile, claiming that Yadav had "doomed" his political career by joining the BJP, the RJD President said he would not press for his resignation from the Rajya Sabha of which he was a member.
"The laid down rules will come into play. If technically he cannot continue as RJD member in Rajya Sabha, the Parliament will act appropriately... The party will not do anything against him," Lalu said and criticised Yadav for calling Narendra Modi 'bhai'.