A former Victorian Greens MP has sensationally resigned from the party, lashing out at what she says is a "toxic" culture within its ranks.

Key points: Samantha Dunn denies her resignation was triggered by her election loss in 2018

Samantha Dunn denies her resignation was triggered by her election loss in 2018 She says the party has been distracted by populism and megalomania

She says the party has been distracted by populism and megalomania She says she will continue to vote for the party

Ms Dunn was the Upper House MP for the Eastern Metropolitan region for a single term, losing her seat at the 2018 election.

In a scathing post on Facebook, Ms Dunn denied her decision to quit was triggered by her election loss.

"I didn't resign because I lost my seat …I resigned because the Greens are too toxic to be part of my life anymore," she said.

"The standard you walk by is the standard you accept, and I'm not prepared to walk by and accept any more of the culture, behaviours and practice I see in the Greens.

"The Greens are distracted by populism, self-interest, power, ego, narcissism, megalomania … while exercising that old-war strategy of divide and conquer."

Ahead of the last election there was speculation the Greens may win enough seats to hold the balance of power in the Lower House.

While the party picked up the seat of Brunswick, it lost the recently gained seat of Northcote and lost four seats in the Upper House.

Ms Dunn said the Greens lacked the ability to "critically self-reflect" on any shortcomings.

"The Greens vote dropped in every Upper House seat, the vote dropped across the state in the Lower House … in the Greens safest Upper House seat, Northern Metro, the vote dropped.

"If this is what success looks like then the benchmark is very low."

Greens beset by scandal

The party's tilt at the federal seat of Batman was derailed by internal allegations of bullying against its candidate, Alex Bhathal.

The Victorian branch later apologised to Ms Bhathal over its handling of the matter, but the six-time candidate resigned from the party, saying she had lost faith in its governance.

In her resignation statement, Ms Bhathal said she believed grievance processes had been weaponised and she had been bullied out of the party.

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The party has had other internal problems.

A staffer accused former Greens leader Greg Barber of sexism, a matter which was settled without Mr Barber conceding the basis of the complaint.

The party's Victorian election campaign was also beset by scandal, with one candidate accused of sexual misconduct and another forced to apologise after using degrading terms in a rap song he wrote about women.

Ms Dunn said the party could not manage conflict and its probity processes lacked the rigour required to preselect candidates.

"The Greens' aversion to conflict resolution means that tensions fester, no-one is ever pulled up for poor behaviours, the behaviours escalate and become legitimised because no-one ever says no or stop it or that's inappropriate," she said.

"The paralysis embedded in the culture of the Greens in terms of dealing with poor behaviours has created a toxic mire."

In a statement, the party's co-conveners said they were disappointed Ms Dunn had left the party.

"Samantha is a committed activist dedicated to saving Victoria's forests and protecting the environment and we wish Samantha well for the future," it said.

"As is normal practice, the party is conducting a review into the 2018 state election, and is committed to learning the lessons from that campaign."

Responding to a question on her Facebook post, Ms Dunn said she would continue to vote for the party.

Editor's Note (15/03/2019): An earlier version of this story said Greg Barber had conceded a complaint of sexism against him was true. This is not correct. The story has been amended.