"There is a sky high difference between Nitish Kumar and morality. If he was moral enough, then after separating with the BJP, he would not have run the government with the support of the Congress party because he had been fighting against them his whole life," said Giriraj.
"This is mere drama, set up to put mental pressure over the legislators and I am saying it in advance that for power, he will compromise with anybody and we will see the consequences by the evening," he added.
Bihar Chief Minister Nitish Kumar had on Saturday resigned taking moral responsibility for the rout of his Janata Dal (United) in the state in the Lok Sabha elections. He however did not recommend dissolution of the assembly.
Meanwhile, JD(U) MLAs will meet in Patna on Sunday to choose their leader and decide the party's future course of action.
Janta Dal (United) president Sharad Yadav has said a new government led by JD(U) will be formed in the state.
Talking to reporters in New Delhi, Sharad Yadav said his party is ready to sink differences with RJD Chief Lalu Prasad for forming a secular alliance government in Bihar.
On Friday, in a terse statement, Kumar said that he "respected the mandate of the people" in favour of the BJP.
In an election where the BJP and JD (U) fought separately after their political divorce in 2013 over projecting Narendra Modi as the prime ministerial nominee of the BJP-led NDA, Nitish Kumar's party could win just two seats.
In the 243-member Bihar Assembly, JD(U) has 115 members, BJP 89 and RJD 21.
JD(U) has the support of four members of Congress, one of CPI and two Independents. There are six vacancies.