The letter was issued by the Special Branch of the Bihar Police on May 28 whereby it directed police officers to gather detailed information including names and adresses of the state functionaries of the Rashtriya Swayamsevak Sangh (RSS) and its subsidiary outfits, including the Vishva Hindu Parishad, Bajrang Dal and Hindu Yuva Vahini.

After the letter came to light late on Tuesday, most of the Bharatiya Janata Party (BJP) leaders, including ministers in the Nitish Kumar-led government, expressed their displeasure and demanded action against the police officer who issued the letter.

BJP MLAs Nitin Navin and Sanjay Saraogi and one MLC Sanjay Paswan have opposed the move.

"Why the police wants information of RSS leaders, who are nationalists and committed to work for the betterment of the nation and the society. It is highly objectionable, we oppose it," Saraogi said.

He said a probe should be conducted into what made the Bihar Police gather information on RSS leaders.

"Action should be taken against the police officer who issued such a letter," he said.

Police authorities are mum on the issue. Even JD-U leaders did not comment on the matter.

The BJP leaders were also surprised that the senior officers assigned to field duty were asked to treat the letter, copies of which were also forwarded to the ADG, IG and DIG of Special Branch, as urgent and provide the relevant information within a week.

According to officers at the police headquarters here, the Special Branch, which is the intelligence wing of the state police, directly briefs the Chief Minister, who is also the in-charge of the home ministry on sensitive issue.