Ghosh, 69, was battling lung cancer for the past five years.
A host of Marxist leaders paid their last respects to Ghosh at the hospital while Left Front Chairman Biman Bose and Communist Party of India-Marxist state secretary Surjya Kanta Mishra condoled his death.
Ghosh had been associated with Jyoti Basu since 1977, the year he became the Chief Minister, and remained his closest aide till the nonagenarian leader slipped into a coma in hospital where he died on January 17, 2010.
Basu had handpicked Ghosh as his confidential assistant. He exerted colossal clout in the corridors of power in West Bengal and finalised Basu's appointments. He communicated between the Chief Minister's Office and the CPI-M state headquarters at Alimuddin Street.
After Basu stepped down as the Chief Minister, Ghosh was officially designated his personal assistant for life.