He was 91 and a bachelor.
A freedom fighter, Viswambharan had participated in the Quit India Movement.
He was also active as a trade union leader and had strived for the rights of Coir workers and had undergone imprisonments four times for participating in various agitations.
During 1946-58, he had worked as a journalist for various publications from Thiruvanthapuram.
Viswambharan, who was a member of the erstwhile Travancore-Cochin legislative assembly in 1954-56, also became a member of the Kerala Legislative Assembly during 1960-64.
Viswambharan was also the first convenor of the Left Democratic Front (LDF), formed in 1973. Condoling his death, Chief Minister Pinarayi Vijayan said his performance as an MP and member of the state assembly was a model for everyone.
He had also made his mark as a journalist and a trade union leader, Vijayan said in a statement. Leader of the Opposition in the assembly Ramesh Chennithala said the passing away of Viswamabharan was a loss to the state as he stood for value based clean politics. Kerala Union of Working Journalists (KUWJ) also condoled his death.