The ACT Young Labor president has resigned from his job as a federal staffer after an internal party investigation found he and two senior Young Labor members had bullied a fellow member, calling her a "rat" and pledging to make her life hell.

Key points: Nick Douros resigned from his role as a staffer to an ACT Senator after the bullying claims were upheld

Nick Douros resigned from his role as a staffer to an ACT Senator after the bullying claims were upheld The victim claims she was targeted by Mr Douros, Francis Claessens, and Niall Cummins

The victim claims she was targeted by Mr Douros, Francis Claessens, and Niall Cummins An internal disputes tribunal upheld that the men had contravened the party's code of conduct

Nick Douros was suspended from his role in the party and quit as a staffer to Senator David Smith after the internal disputes tribunal upheld an allegation he and two others — ACT Young Labor conduct contact officer Francis Claessens, and Niall Cummins — had contravened the party's code of conduct.

Mr Claessens and Mr Cummins were also suspended from their positions and all three men were ordered to attend mediation and undergo respectful behaviour training.

The victim — who made the complaint to ACT Labor in August last year — alleged she was targeted as a result of an internal party stoush during the pre-selection process for Canberra's three federal lower house seats.

The Construction, Forestry, Mining and Energy Union (CFMEU) ordered its staff to join the party's left faction and Mr Douros, Mr Claessens and Mr Cummins believed the woman would quit the centre coalition.

Online chat logs, which the victim obtained, showed Mr Cummins asked a group whether the woman could be ejected from Young Labor.

In reply, Mr Douros wrote: "Tbh we can just bully the f*** out of her until she does" and called her "weak".

Mr Douros was an advisor to ACT Labor Senator David Smith (pictured). ( ABC News: Marco Catalano )

Mr Douros later texted the woman to demand her resignation and proxy her spot at the ACT Labor Conference.

When she ignored the demand, Mr Douros told the other men he would make her life hell if she did not comply.

At the conference, the victim was called a "rat" when she walked past a group, which included Mr Douros and Mr Claessens.

Mr Douros, Mr Claessens and Mr Cummins did not respond when contacted for comment.

Senator Smith's office confirmed Mr Douros had resigned from his employment after the allegation had been upheld.

ACT Labor secretary Matt Byrne said he could not comment on internal matters.