The Greens have launched an inquiry into the failed Batman byelection campaign to find those responsible for “backgrounding and leaking of sensitive and confidential party matters”.

The leaked terms of reference for the review, seen by Guardian Australia, appear to assume that damaging leaks accusing the Greens candidate, Alex Bhathal, of bullying constituted a breach of confidentiality and widen the investigation to members’ public discussions of the issue.

The 101-page internal complaint by 18 party volunteers that emerged during the campaign alleged that Bhathal had engaged in misconduct including “systematic intimidation, and malicious and reckless false statements about members and party decisions”. Bhathal denied the allegations.

The Greens leader, Richard Di Natale, has suggested that those responsible for the leak should be expelled from the party, describing it as a “major factor” in the loss.

The review’s terms of reference promise to investigate “tension in the Darebin branch” and the “overall risks” to the Greens arising from the loss.

It will investigate how confidential information is provided to the state executive and “the impacts the breaches of confidentiality had on the candidate, other individuals, Darebin branch, Batman byelection results and [the Australian Greens Victorian branch] as a whole”.

In a sign the leaks will be blamed for the loss, the review will consider “the interplay between internal party matters and the political strategy and electoral results”.

Also up for investigation is “public messaging” regarding the party dispute and whether members’ comments on social media constituted breaches of the code of conduct.

The review, which will report by 24 May, will “aid party leaders and decision makers instigate any recommended actions on members, processes or party structures”.

In March the former Greens Western Australia convener Grahame Bowland warned that the review could constitute a “purge” that would not be limited to people responsible for the alleged leaks in Batman.

Bowland called on Di Natale to resign, saying it was “manifestly unhelpful” that he had prejudiced the outcome of internal investigations.

On Friday, the Greens Victoria co-conveners Rose Read and Colin Jacobs wrote to members acknowledging that many were “concerned with how an ongoing conflict in the Darebin branch has become so public in recent weeks”.

They said the Batman byelection had been “marred by an unfortunate leak” and that in recent days “further leaks and damaging allegations have been aired by people within and outside the party”.

Read and Jacobs promised to investigate and “find a way forward to defuse some of the tensions”. The pair encouraged members to “be sceptical of what they hear in the media or via third parties, to trust in party processes and give fellow members the benefit of the doubt”.

“Significant damage has been done to the reputations of longstanding Greens members without the benefit of any proper, transparent and just process.”

They urged the Greens not to abuse or harass fellow members, including by “further spreading possibly unfounded allegations”.

Fairfax Media had reported this month that the 18 members responsible for the complaint survived a push to pressure them to resign from the party at a branch meeting.