Congress president Mallikarjun Kharge on Thursday accused Prime Minister Narendra Modi of tarnishing democracy by not speaking in Parliament and instead making political speeches outside.
He said the country has not seen a "darker period than this" in the history of its parliamentary democracy.
Kharge also dubbed the central government as a "blot on humanity" for its "indifference" towards Manipur, which he said was "burning" for the past 85 days.
People have now become aware and will fight "this kind of politics", he said.
"Parliament session is going on and instead of speaking on the floor, the prime minister is making speeches here and there. By doing so he is tarnishing democracy. The misdeeds of the Modi government cannot be erased by calling opposition parties names," Kharge said.
The Congress chief also hit out at the BJP, accusing the party of not allowing him to speak in the Rajya Sabha and for jeering at opposition members for wearing black clothes in Parliament as a mark of protest over the Manipur issue.
"Only those having a mindset against Dalits, tribals and backward people can make fun of black clothes. But for us, black is a symbol of protest and strength.
"Black is a symbol of justice and dignity. The people of Manipur deserve justice, peace and respect," he said in a tweet in Hindi.
Opposition members on Thursday wore black clothes as a mark of protest for not allowing them to raise the Manipur issue in Parliament.
Kharge said the BJP cannot run away from its responsibility after plunging life in Manipur into "darkness", by adopting a "Dictatorial attitude" and by diverting people's attention from the issue.
"You do not want to talk in Parliament -- the temple of democracy -- and want to give a political speech in Rajasthan while opening new medical colleges," Kharge told reporters while slamming the prime minister outside Parliament.
He said Manipur burning is a "black chapter" for the country. The government, which did not take care of the weeping people of Manipur in the last 85 days, "is a blot on humanity".
Congress general secretary Jairam Ramesh said, "The prime minister has all the time in the world to bunk Parliament just to duck debate on Manipur while hurling abuses and his brazen brand of lies at the Congress party in election rallies in Rajasthan and elsewhere."
"It is so pathetic that he will not even make a statement inside Parliament on the horrific tragedy that has all but destroyed Manipur," he said on Twitter.
The opposition has been accusing the prime minister of not making a statement in Parliament on the northeastern state, which has seen violence since May 3.
Both Houses of Parliament have not been able to transact much business amid the uproar caused by the opposition which has been demanding a statement from the prime minister on Manipur and a discussion thereafter.
