The battle for the Labor preselection in the ultra-safe federal seat of Gellibrand has turned nuclear, with vicious shit sheets circulating sledging candidates, and the retiring MP — former attorney-general Nicola Roxon — responding with a personal missive damning the attack.

The bright red sheet, mailed to local members and obtained by Crikey, contains noxious and incorrect claims relating to candidate and former Roxon staffer Katie Hall’s history as an organiser at the Health Services Union.

It inexplicably says Hall had a “direct and active involvement in Australia’s biggest union corruption scandal” and says, apropos of nothing, she was involved romantically with former branch secretary Jeff Jackson. The missive has shocked locals, and rival campaigns were rushing to distance themselves from its content this morning. Some stylistic elements of the letter appear to have been culled from a short-lived YouTube video attacking noted Watts supporter Victorian Senator Stephen Conroy (not online).

In an email to members, arch rival Kimberley Kitching said she “categorically” denied authoring the sheet and:

“…would certainly be willing to swear to it on my oath. I don’t like that type of campaigning, I believe it to be wholly ineffective in any event.”

With five candidates, Gellibrand is one of the most vigorously fought contests of recent times because, with a margin of 23.9%, the vote will effectively anoint a Labor member to Capital Hill in perpetuity. The Gellibrand battle is a showdown between Hall, popular tweeter and senior Telstra corporate relations staffer Tim Watts, former Melbourne City Councillor Kitching, alternative Labor Unity candidate Julia Mason and local unaligned contender Daniel McKinnon.

A local Hall-leaning branch member said that the sheet was designed “to muddy the waters and deter rank and file voters from voting in the preselection because they’re ‘disgusted’ with the process. But they’re smarter than that and it hasn’t worked.”

The local vote, making up 50% of the final result, will resume at 6pm tonight at Sheldon Receptions in Sunshine West before the central Public Office Selection Committee rules on the other 50% tomorrow.

Roxon’s response — also obtained by Crikey — slams the “horrid” jihad on Hall and urges local preselectors to marshal their anger to “reject s-xism in Gellibrand”. Roxon wrote:

“I’m disgusted at some of the malicious, nasty and false materials that have been distributed in the last days of the preselection campaign, in what has otherwise been a hard fought, yet dignified, contest.

“It is frustrating that every time a capable woman puts up her hand to run for office, she has to deal with false allegations about her s-xual history.  We might expect this misogyny and s-xism from our Liberal opponents, but surely it has no place within modern Labor?”

The sheet came just one day after another sheet, purported to (but almost certainly not) have been sent by unaligned candidate Daniel McKinnon, rubbishing the other four contenders.

“It was a low-level summary of rubbish about Katie, intimating Mason was a [Michael] Danby puppet,” one senior campaign source said. It also appears to have vastly overestimated Watts’ Telstra salary.

The mechanics of the vote are intriguing. Local voting will conclude tonight before the state 100-member POSC convenes to decide the winner. Of crucial importance is a binding pre-POSC Labor Unity caucus, which will decide where its 24 POSC votes go. A “stability pact” with the Socialist Left will then elevate the total numbers in support the Unity candidate to well over 60.

The 404 local votes will be normalised to 100 votes before preferences are allocated, making how-to-vote cards crucial. Hall and Watts are swapping preferences, with Kitching going first to Mason and then Hall. Sources said this morning that Hall appeared to have done well in the local ballot so far and that Watts’ path to victory would rely on a first or second placing in the grassroots vote, followed by a majority inside the Unity caucus. Watts is believed to have the internal Unity numbers.

The split in the so-called “ShortCons” is the first sign of internal tension between Conroy and his lower house soulmate Bill Shorten for years. It is significant because the fissure has the potential to spray blood over every winnable preselection for the foreseeable future, further damaging Labor’s brand in the eyes of the public.

Other senior Labor figures have been bold in their voting intentions. Yesterday, former Victorian premier and Gellibrand local Steve Bracks turned up to vote and was approached by Kitching brandishing her how-to-vote card. Bracks apparently retorted “never from you” and kept walking.