Ho also suffered head injuries and needed stitches after the men beat him with rods, the party said, adding that this was clearly a planned attack against those who hold different political views.
Ho later said in a post on his social media account that he will have to undergo surgery later, and called on any witnesses to come forward.
The party condemned the assault, describing it as a form of ‘white terror.’
Ho is the latest in a a series of pro-democracy and localist figures who have been attacked over the past six weeks – some of whom had organised anti-extradition rallies.
They include Ronald Leung, Max Chung, Jimmy Sham, lawmaker Roy Kwong, Chan Ho-tin, Isaac Cheng, as well as a female Apple Daily journalist who has been covering the protests.
Ho made a name for himself for organising a dock worker strike back in 2013, and recently lost in a rural committee election.