Six months after the ABC Four Corners aired a program on turmoil within the Australian Greens, a factional war has been ignited over comments by a senior Greens MP.

Federal senator Lee Rhiannon has backed a complaint made about Greens NSW Upper House MP Jeremy Buckingham, that calls for him to be expelled or suspended from the party.

It claims in the Four Corners report he made "serious and false criticisms" about both the NSW Greens and members by criticising the actions of Ms Rhiannon and her faction, as well as relaying a discussion he had with Ms Rhiannon's partner Geoff Ash.

Mr Buckingham has hit back in a letter to Australian Greens Convenors and MPs slamming the complaint as seeking "to usurp the grassroots preselection ballot for the 2-19 NSW state election Upper House ticket".

Mr Buckingham will go up against Ms Rhiannon's factional ally, David Shoebridge, for the top spot on the ballot.

Last November Lee Rhiannon lost her top spot on the Senate ticket for the next federal election.

The complaint was submitted to the Greens NSW Convenor who was urged by the complainants not to arrange mediation.

"We believe that mediation would be a waste of every ones' time, and do not agree to it," the complaint said.

Mr Buckingham has engaged legal counsel who says the Greens MP is being denied procedural fairness because the issue is capable of mediation.

His lawyer is also pushing for the "full voting membership of the NSW Greens" to decide whether Mr Buckingham is expelled, instead of a random selection of four members as is the normal process.