Occupy Movement leaders Joshua Wong, Nathan Law and Alex Chow along with some lawmakers held a demonstration outside the Correctional Services Department on Tuesday, demanding immediate reforms to the city's prisons.
They held a banner and placards outside the headquarters of the department in Wan Chai, saying inmates should not be denied of their rights and dignity.
The protest follows a string of physical and psychological abuse allegations made by former inmates.
Wong also officially filed a complaint to the department over what he said was humiliating treatment when he was transferred to Tung Tau Correctional Institute in October. He alleged that he was stripped naked, made to squat down and then answer questions from guards.
The leader of the Demosisto party said it was unnecessary for officers to treat him in that manner.
Disqualified lawmaker Law and former secretary general of the Federation of Students Chow also submitted their views on how to make improvements to prison life.
The trio were jailed over a protest in 2014 which sparked the 79-day Occupy sit-ins. They are currently on bail while waiting for an appeal against their prison terms, which they were given after the government appealed against non-custodial sentences handed down by a lower court.
In response, the Correctional Services Department said its officers take care of the basic needs of inmates and their treatment is subject to reasonable and appropriate limitations.
A spokeswoman added that the department's complaints unit deals with each complaint in a fair and objective manner. She said the department welcomes comments on its operations, but she did not say whether the commissioner will meet the reform campaigners.
Last updated: 2017-11-21 HKT 18:43