Karat, who is in the Kerala capital, said Mukherjee devoted his entire life for the revolutionary movement in India and had played a vital role in building the party and the trade union movement in the country.
The participants at a seminar held here in connection with the golden jubilee of the party's ideological journal "Chintha", where Karat was the main speaker, observed a minute's silence as a mark of respect towards the departed leader.
"Mukherjee was the senior most leader of Indian revolutionary movement who turned his life into a ceaseless struggle by firmly holding on to Marxism and Leninism", Vijayan, also a polit bureau member said.
He recalled that Mukherjee also distinguished himself as an able parliamentarian and astute trade union leader.
The centenarian CPI(M) leader died of old age ailments today at Kolkotta.