Speaking on the party's lone Rajya Sabha MP Birendra Prasad Baishya voting in favour of the Bill in the Upper House, Kalita said, "We had never supported the CAB but, yes, our RS MP voted for it and that raised several questions in the people's mind".
The third day of protests against a new law in India - which would give citizenship to people from neighboring countries fleeing religious persecution unless they are Muslim - turned violent as demonstrators lit buses on fire and fought with police.
At least 15 metro stations in Delhi were closed on Sunday as a result of violent protests.
Anger with Modi's Hindu nationalist government was further fuelled by allegations of police brutality at Jamia Millia Islamia university on Sunday, when officers entered the campus in the capital New Delhi and fired tear gas to break up a protest.
Mr. Singh on Thursday had said the Citizenship (Amendment) Bill was a direct assault on India's secular character and Parliament had "no authority" to pass a law that "defiled" the Constitution and violated its basic principles.More news: Los Angeles Kings travel to Detroit to take on the Red Wings
Students insisted in a statement that they disassociated themselves from any violence.
Some protesters shared videos that apparently showed policemen causing destruction of property amid the protests. While police maintained that it did not open fire, one of the protesters admitted in the Holy Family hospital was found to have a bullet injury in the leg.
What has the reaction been in other Indian cities?
Students said they also stood in solidarity with fellow student in Delhi who clashed with police in Delhi on Sunday.
Many students from the storied Muslim university have been protesting against the new law since Friday, when police first used tear gas to disperse protesters.More news: The Hallmark Channel Pulls Ads Featuring Same-Sex Marriage
A large protest also broke out in the southern city of Hyderabad, as students of Maulana Azad Urdu University carried slogans against the police action in Delhi. It applies to migrants from Afghanistan, Bangladesh and Pakistan, all of which are majority-Muslim nations.
The legislation, passed by parliament on Wednesday, allows Delhi to grant citizenship to millions of illegal immigrants who entered India from three neighbouring countries on or before 31 December 2014 - but not if they are Muslim.
The UN human rights office said last week it was concerned the law "would appear to undermine the commitment to equality before the law enshrined in India's constitution".
The government denies any religious bias and says Muslims are not covered by the new law because they are not religious minorities, and therefore do not need India's protection.
They argue that outsiders will take over their land and jobs - eventually dominating their culture and identity. At least 50 people were injured in the protest, including cops.More news: Rep. Steve Cohen: Trump-Ukraine Call ‘an Affront’ to MLK’s Memory