He died of cardiac arrest at a hospital near New Delhi on Friday, his party said.
"Comrade Harkishan Singh Surjeet died at 1.35 p.m. today after a cardiac arrest," the party said in a statement on its website.
Singh, 92, a former general secretary of the Communist Party of India (Marxist), was ill for several months.
Surjeet firmly believed that only a strong CPI(M) can help create a viable third alternative, based on a common policy platform to conduct joint struggles rather than just an electoral alliance, to foist what he called a "people's government" at the Centre.
Elected as CPI(M)'s General Secretary in 1992, a post he held till 2005, he is also seen as a mentor to leaders like Prakash Karat, who succeeded him, and Sitaram Yechury besides a bridge between the old and new generation comrades.
Surjeet remained a father figure for partymen till the end.
The grand old man of the Indian Communist movement was instrumental in making the Left bloc extending key outside support to the Congress-led UPA government headed by Manmohan Singh in the wake of a fractured verdict in 2004 Lok Sabha elections, thus averting the possibility of snap polls.
