RJD said that historian Ramchandra Guha had talked once about Nitish Kumar as fit to become PM.
More political parties and film bodies on Sunday demanded the withdrawal of the controversial sedition case filed against 49 celebrities after they had expressed concern over rising incidents of mob lynching in an open letter to Prime Minister Narendra Modi.
The CPI(M) and the Kerala State Chalachitra Academy joined the DMK, the Congress and others in condemning the filing of the case against celebrities like Aparna Sen, Adoor Gopalakrishnan, Ramchandra Guha, Mani Ratnam, Anurag Kashyap and Revathi.
The Communist Party of India (Marxist) said this reflects the "growing authoritarianism" in the country. "This is tantamount to punishing all those who have a dissenting opinion on the policies of the present government. This is a complete negation of democratic rights and reflects the growing authoritarianism in the country," the Left party said.
The Kerala State Chalachitra Academy called it a "blatant violation" of the freedom of expression guaranteed under the Constitution.
The case was registered after a chief judicial magistrate in Bihar''s Muzaffarpur passed an order on a plea by a lawyer alleging that the celebrities had tarnished the image of the country through their open letter.
Asked about the case, Union minister Prakash Javadekar Saturday said the government has nothing to do with it. "An individual went to the court which has passed an order."
But Adoor Gopalakrishnan, one of the writers of the letter, has said the registration of a sedition case is a "matter of great concern".
The filmmaker cited an incident where, he said, a woman and her followers were found shooting at Mahatma Gandhi's effigy on January 30. "None of them have been labelled as anti-nationals, with even some of them managing to become MPs."
On Saturday, DMK chief MK Stalin, Congress leader Digvijay Singh, RJD national vice-president Shivanand Tiwary and the CPI had demanded that the sedition case be withdrawn.
A day before, the Congress party had urged "all right-thinking progressive" parties to collectively "fight this growing spectre of authoritarianism".
"Where is this country headed? People of India need to seriously think, need to seriously apply their minds to what is happening to this country in the past 120-odd days ever since the NDA-BJP government assumed office," Congress spokesperson Manish Tewari said.
Mr Stalin said labelling celebrities anti-national for expressing their concern was unacceptable. "How can seeking to uphold the basic tenets of the Constitution like tolerance and communal harmony be construed as anti-nationalism," he asked in a statement.
The CPI said it firmly stood for independent judiciary but cases like this were bound to strengthen the apprehension that judicial systems are used to harass and intimate the critics of the present government.
"Adoor Gopalakrishnan is someone who has always upheld human values through his movies. The act of registering a case against those who had expressed concern over the growing action against humanity does not go well along with a civilised democratic society," the Kerala Chalachitra Academy said.
RJD's Shivanand Tiwary, who was formerly with the JD(U) headed by Bihar Chief Minister Nitish Kumar, said in a statement that historian Ramchandra Guha had raved about Nitish Kumar as a leader fit to become the prime minister.
"It is ironical that Guha finds himself booked for sedition in the very state ruled by Kumar. I would urge Nitish Kumar to seek legal opinion and get the case annulled," he said.