The condition of veteran All India Forward Bloc leader and state party secretary Ashok Ghosh continued to be critical on Wednesday, doctors said.
Ghosh, the Left Front leader in West Bengal, was rushed to a city hospital on Tuesday and put on ventilator support.
Ghosh, 94, was admitted to the hospital following lower respiratory tract infection.
"He continues to be on ventilator support. His condition is critical but under control," said a doctor.
West Bengal Chief Minister Mamata Banerjee and Left Front chairman Biman Bose were among those who visited him to the hospital and inquired about Ghosh's health.
Ghosh has been a long-time state general secretary of the party founded by Netaji Subhas Chandra Bose.