Nur Hossain Kasemi, secretary-general of Hefazat-e-Islam Bangladesh, is in critical condition.
He is presently undergoing treatment at the Intensive Care Unit (ICU) of the capital's United Hospital, Daily Jugantor reported.
"A medical board will meet today to decide on the future course of his treatment," said Munir Ahmed, press secretary of Kasemi.
The Hefezat leader was admitted to the hospital with breathing difficulty on 1 December. Later on 10 December evening, he was moved to the ICU as his physical condition deteriorated.
Kasemi served as the party's Dhaka city unit president before being appointed as the secretary-general of Hefazat-e-Islam in November this year following its supreme leader Shah Ahmad Shafi's death on 18 September.