"Now the challenge is that the right wing forces have captured political power and they are posing a 'grave threat' to the country's integrity, secular fabric and the Constitution," he said here.
He was addressing a public meeting to mark the celebrations of the 90th anniversary of foundation of CPI.
RSS and Sangh parivar outfits have become "very aggressive and offensive," Raja said adding they want to 'subvert' the present political system.
"It is a big challenge and Communists have to fight this challenge...The situation demands that Communists and Leftists should come together and unite and fight against these reactionary forces. Communists unity has become a historic necessity," he said.
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The corporate sector had become powerful, deciding policies of sucessive governments, he charged accusing the Narendra Modi government of protecting them.
The 'Make-in-India' slogan was nothing but an invitation to multinational corporates to come and make profit in the country, he said.
The situation demands that Communists should reach out to working people and mobilise them to save the country, he said.