Ghannouchi, 82, a fierce critic of President Kais Saied and head of the Ennahda main opposition party, was jailed last year on charges of incitement against police and plotting against state security.
Earlier this month in a separate case a judge sentenced him to three years in prison on charges of accepting external financing.
"While he is fighting the 'empty stomach' battle, Ghannouchi calls on Tunisians to adhere to a democratic Tunisia that includes everyone on the basis of freedom ... and the independence of the judiciary," the lawyers said in a statement.
The opposition says Saied's sudden shutting down of the elected parliament in 2021 and moves to rule by decree amounted to a coup.
Saied, who enshrined his new constitutional powers in a referendum with a low turnout in 2022, has denied his actions were a coup and said they were needed to save Tunisia from years of chaos.
Six opposition leaders arrested last year in a crackdown began an open-ended hunger strike last week to protest at their imprisonment without trial and demand their immediate release. They called for an end to judicial prosecutions against all politicians, journalists and civil society activists and for intimidation and threats to judges to stop.
The leaders — Jawher Ben Mbarak, Khayam Turki, Ghazi Chaouachi, Issam Chabbi, Abdelhamid Jalasi, and Rida Belhaj — were detained on suspicion of plotting against state security.
The opposition accuses Saied of muzzling the press and imposing authoritarian rule. They say his constitutional changes have pulled apart the democracy built after a 2011 revolution.
Saied rejects those accusations and has called his critics criminals, traitors and terrorists and warned that any judge who freed them would be considered abetting them.
Forum