Days after demanding that the amended citizenship act be scrapped, Nobel laureate Amartya Sen has stressed the importance of opposition unity to carry out any protest for a cause.

However, he said even in the absence of opposition unity, protests can continue.

The economist was talking to journalists in Kolkata over the countrywide CAA-NPR-NRC protests.

'For any kind of protest, opposition unity is important. Then protests become easier. Unity is important if the protest is for a proper cause,' Sen told journalists on Monday night.

'But even if unity is not there, then that doesn't mean we will stop protesting. As I said, unity makes protest easier but if unity is not there still we have to move on and do whatever is necessary,' Sen said.

Earlier, speaking at Nabanita Deb Sen Memorial Lecture, the economist said viewing oppositional reasoning as quarrelsome would be a big mistake.

'It is necessary to emphasise the subtleties of the innovative forces of the opposition... We need to know more about what I am protesting about. The head must also join with the heart in protest,' Sen said in his speech.

'When there seems to be a big mistake in the Constitution or human rights, there will surely be reasons to protest,' Sen said.

Deb Sen, who passed away at her Kolkata residence last November, was the economist's first wife.

A few days ago, Sen, who has been critical of the Narendra Modi-led Union government, said the contentious Citizenship (Amendment) Act should be scrapped.

'I think the CAA must be scrapped because it cannot be an act ... That's the job of the Supreme Court to see whether what was passed in Parliament can be legally attached to the Constitution,' the Nobel laureate had said.