The former Greens candidate Alex Bhathal says she has made the “heartbreaking” decision to quit the membership, a decision that caps a torrid 12 months for the party.

Bhathal, a six-time candidate for the inner-city Melbourne seat of Batman, said in a statement on her website that she had been subjected to “abuses of power and process” and “relentless organisational bullying” over five years.

“I have now come to the realisation that I can no longer subject myself to this continuing organisational abuse,” Bhathal said on Friday. “I am exhausted and worn down and my children have been traumatised. I’m leaving because I need to get out of this awful situation and get my life back.”

Bhathal’s departure comes amid a reported exodus of party members, according to the Age, which cited documents on Friday suggesting one-third of its Victorian members quit in the 21 months to December. Her decision to quit publicly threatens to further inflame internal divisions ahead of the federal election.

Bhathal had been endorsed as the candidate for Batman, now Cooper, for the upcoming election, but stood down last year, saying she was concerned by the prospect of more “sabotage”.

Earlier that year, she had contested Batman against Labor’s Ged Kearney, but her campaign was derailed by an internal campaign against her, including the leaking of a “dossier” of bullying claims.

Announcing she had stood down as the 2019 candidate, Bhathal told Guardian Australia at the time she was “currently receiving legal advice” about potentially launching proceedings under the Incorporated Associations Act.

On Friday, Bhathal revealed she was facing “misconduct charges” at a state council meeting on Saturday as a result of providing that statement to Guardian Australia. She also revealed that the party had re-opened an investigation into complaints against her.

“I want to put on the record that I’ve never engaged in bullying or intimidation of anyone,” she said in her statement on Friday. “During my 18 years in the party, I have had a range of leadership roles. I have had to call out actual poor treatment of and risks to volunteers and members and have challenged actual misconduct and attempts to abuse process.

“I’ve found myself caught up in a bizarre nightmare where I have been accused of bullying and misconduct. The Batman byelection campaign, then the Greens’ best chance to gain a second lower house seat, was viciously undermined.”

Among the allegations reportedly contained in a dossier leaked to the media last year were that Bhathal stood in front of another Greens representative at a press conference, that she unfriended a party member on social media, and that she had made the local Darebin branch an unsafe space.

The Victorian Greens’ November state election campaign was widely viewed as a disaster, as the party struggled to defend itself against attacks on its internal culture.

Ultimately, the party won a new lower house seat in Brunswick but gave up Northcote in a bitter tussle with Labor, while four of its upper house MPs also lost their seats.

The party has been talking up its chances of winning a second lower house federal seat at the upcoming election as it hopes to wrest Higgins from the Liberal party following the resignation of Kelly O’Dwyer.