Wall-fare, a prisoners' rights group, announced on Tuesday that it has disbanded.
Its founder, former lawmaker Shiu Ka-chun, said the group had always been cautious in carrying out its work since it was formed nine months ago, but it "could no longer carry on".
The announcement came a week after Security Secretary Chris Tang said some groups were giving prisoners treats such as chocolate to recruit them to endanger national security.
Shiu stressed that Wall-fare had been doing humanitarian work.
“What support will the prisoners get without Wall-fare? We can’t tell today. We only wanted to do the humble work – to give a cup of cool water to the prisoners and their family. Unfortunately, this cup of water may have become too hot now,” he said.
Shiu said all the members agreed on Sunday to dissolve the group, but he refused to say whether the move was down to political pressure.
"We can't say more. I'm sorry. I think we all understand what's happening."