The civil society groups met under the banner of 'Janadhikar Sangharsh Samiti', to protest what it called the government's "frontal attack on the Right to Expression, Association and Dissension".
In a crackdown on NGOs receiving foreign funds, the government has cancelled licences of nearly 9,000 such entities for violation of the Foreign Contribution Regulation Act (FCRA).
Slamming the government action, the organisations at the meeting pledged to explore all possible legal options as part of their fight against the crackdown.
She said time has come to take action to "reclaim democratic political space for dissent" and vowed to continue the fight "till the end".
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Pillai also shared her experience of government crackdown on Greenpeace as well as being stopped at New Delhi airport from boarding a flight to London.
Javed Anand of Sabrang trust, with which civil rights activist Teesta Setalvad is also associated, accused the government of following an "authoritarian ideology".
Professor Achin Vanaik of Coalition for Nuclear Disarmament and Peace (CNDP) said it was necessary to protect the minorities. "By minorities, we do not mean only religious minorities, but also dalits, tribals, and all those deprived sections who have suffered much during their fight for livelihood," Vanaik added.