Bharatiya Janata Party (BJP), an ally of Bihar's ruling JD-U, is the political arm of the Rashtriya Swayamsevak Sangh (RSS).
The letter was issued by Superintendent of Police (Special Branch) on May 28, two days before the swearing-in of the BJP-led Narendra Modi government at the Centre.
"It is a serious matter and I raised it in the Legislative Council. The government must explain how and why the police wanted information about leaders of RSS, the country's largest nationalist organisation," Mayunkh told .
A day after the reports about the letter came out, leaders of the BJP,expressed their displeasure and demanded action against the police officer who issued it.
The BJP leaders also expressed surprise that the Deputy Superintendents of Police, to whom the letter was sent, were asked to treat it as urgent and provide the relevant information within a week. Copies of the letter were also forwarded to the ADG, IG and DIG of the Special Branch.
According to officials at the Police Headquarters here, Special Branch is the intelligence wing of the Bihar Police and directly briefs the Chief Minister, who is also in charge of Home.
A senior RSS leader, on condition of anonymity, said it appeared that the state police issued the letter only after a go-ahead from above. "It is something not normal as we are working among public, not hiding anything," he said.
BJP MLA Sanjay Savargi said it must be probed what promoted the Bihar Police to issue the letter.
"Why does the police want information on RSS leaders, who are nationalists and committed to work for the betterment of the country and society? It is highly objectionable," said BJP MLA Nitin Navin.
However, the opposition Rashtriya Janata Dal (RJD) and Congress leaders have praised Chief Minister Nitish Kumar and welcomed the state police move to gather information about RSS leaders in the state.
( With inputs from IANS )