Senator David Smith's office has confirmed one of his staffers has resigned from the office after an internal party investigation upheld claims against him.
The findings of the investigation were handed down earlier this year, but it is unclear when Nick Douros resigned from his position in Senator's Smith's office.
A spokesman for Senator Smith would only confirm Mr Douros had resigned after the findings were handed down, but gave no indication of when that was. Mr Douros had been seen in the halls of Parliament House in recent days.
Mr Douros was accused of bullying, along with Niall Cummins and Francis Claessens, after a series of messages in a group chat last year, where members had called another member a "rat" and promised to "bully the f--- out of her" in a bid to force her to quit her role in the party's youth branch.
All three have been ordered to attend mediation and respectful behaviour training, and suspended from any party positions they held. Mr Douros had been president of ACT Young Labor.
The complaint was made to ACT Labor and referred to an internal tribunal in August last year in the middle as part of the fallout from factional power plays within the party.
Legislative Assembly member Michael Pettersson announced he was leaving the Right faction of the party after the Construction, Forestry, Mining and Energy Union demanded all its staff join the Left faction.
Mr Pettersson worked for the union before he was elected in 2016, and the CFMEU backed his preselection even though he was then part of a rival faction.
Some other CFMEU staffers also left the Right along with Mr Petterson, but it is unclear if any of them have been officially accepted into the Left. The target of the messages was part of a group that was believed to be changing factional allegiance.
Mr Douros, Mr Claessens and Mr Cummins have been contacted for comment.
ACT Labor secretary Matt Byrne didn't comment on the issue.