Senior party leader Anand Sharma said that the reason for opposition is not political but constitutional and moral.
"I am convinced that the bill you (Home Minister Amit Shah) have brought is an assault on the very foundational value of Indian Constitution," Sharma said while participating in the debate on the bill.
The proposed legislation provides for giving Indian citizenship to the members of the Hindu, Sikh, Buddhist, Jain, Parsi and Christian communities who came to India from Pakistan, Bangladesh and Afghanistan after they faced religious persecution in those countries. Once the bill is passed, they will not be treated as illegal immigrants, and will be accorded Indian nationality.
The Congress and some other opposition parties such as Trinamool Congress and CPI have termed the bill against the spirit of the Constitution which treats people from all religious and faith as equals.
As the Citizenship Bill seeks to grant Indian citizenship to non-Muslim refugees from Pakistan, Bangladesh and Afghanistan, they have said it is discriminatory.
"It is against our democracy. It fails the morality test. It is divisive and discriminatory," Rajya Sabha member Anand Sharma said.
After a marathon and heated debate, the Lok Sabha, where the BJP is in majority, passed the controversial bill last Monday (December 2).
Home Minister Amit Shah on Wednesday introduced the bill in the Upper House where the members would discuss the bill before approving or disapproving it. Some of the members from opposition parties have demanded to send the bill for scrutiny to a House panel. They have also moved amendment for the same.
While introducing the bill, Shah termed the bill historic and said it offers a ray of hope and a new beginning to lakhs and crores of people who have been living a life of extreme hardship and misery for years. He also said that the bill fulfils the promise made by the BJP in its Election Manifesto.
( With inputs from IANS )