The party also said that Maharashtra Chief Minister Prithviraj Chavan should also should step down owning the moral responsibility of Congress' defeat in the state.
"In the recent Lok Sabha polls, the Janata Dal (United) was decimated in Bihar. Owning the moral responsibility of the party's defeat, Nitish Kumar gave his resignation as the Chief Minister.
The 'Modi tornado' swept across Bihar so strongly that not only JD(U), but Lalu Prasad Yadav's RJD and Congress were reduced to ashes," the Sena said in its mouthpiece 'Saamana'.
"After Narendra Modi was declared BJP's Prime Ministerial candidate, Nitish Kumar severed ties with the NDA, fearing that the Muslims and Dalits in Bihar would stop supporting the party.
"Quite contrary to it BJP gained in the Muslim-dominated constituencies in Bihar and won with a thumping majority. So what did Nitish Kumar gain by opposing Modi? Had he remained with the NDA, he would not have faced such a humiliation," it said.
The party, which won 18 seats in the recent Lok Sabha polls, also said that since all his political decisions went wrong, Nitish Kumar has now become frustrated.
"Though Nitish Kumar did the 'nautanki' of giving resignation, he did not recommend the dissolution of the state assembly saying that he does not want to push Bihar into political instability. But Nitish Kumar is now holding meetings with Lalu Prasad Yadav and there is a talk that they may come together to counter Modi. Though Nitish has stepped down on moral grounds, what can be more immoral than joining hands with Lalu Yadav?" the party said.
Targeting the Congress-led Democratic Front government in Maharashtra on the same issue, the Sena said, "Though Nitish at least did this resignation drama, the Congress-NCP led government is not even doing that.
Congress has been completely wiped out in Maharashtra. While the victory of Ashok Chavan is his personal, party's win in Hingoli is a mere accident."
Pressure is building on Prithviraj Chavan to resign. This pressure is also from within the party. Even the Chief Ministers in Uttarakhand, Assam and other Congress-ruled states are not quitting despite the defeat, it said.
Criticising the Aam Aadmi Party (AAP), the Shiv Sena said, "The AAP government in Delhi had resigned on the moral grounds and then contested the Lok Sabha polls. However, after a poor show in the elections, it is back in Delhi to tap the possibility of forming a government. They think that public mandate is a child's play."