A long-time Liberal member has threatened to tear the party apart and push fellow members to Cory Bernardi’s Australian Conservatives if the Warringah motion for one member-one preselection vote does not succeed this weekend.

The motion will be debated at the NSW Liberal Futures convention in Sydney, an unprecedented event called specifically to discuss the party rules.

The convention will be open to the media to hear Malcolm Turnbull and the NSW premier, Gladys Berejiklian, address 1,500 registered members before the convention closes to discuss the contentious rule changes.

John Howard recommended plebiscites following his review of the party after he left office. Turnbull favours more open preselections but has not backed any particular model.

John Ruddick has been campaigning for all members to vote in their local preselections since 2011. He said the only good outcome was the defeat of all motions apart from the Warringah motion.



He labelled attempts by Liberal MPs Julian Leeser and Alex Hawke to broker a compromise as a con. The Leeser/Hawke motions would place eligibility criteria on members such as activity tests and waiting times before being eligible to vote, and would protect sitting members from the new system with a grandfather clause.

Opponents of Warringah say that this would reduce the chance of branch stacking, though no Liberals would talk on the record as it is against party rules. Ruddick is no longer a party member.

“If the Hawke/Leeser ‘con-job’ compromise motions are supported, then I will be joining Cory Bernardi’s Australian Conservative party on Sunday afternoon and will launch a high-velocity campaign to bring as many Liberal party members as possible to join me,” Ruddick told Guardian Australia.

“I single-handedly launched the democracy campaign within the NSW Liberal party and I will gladly tear it apart if they explicitly reject simple democratic principles.”

The outcome may feed Bernardi’s plans to cannibalise the Liberal party membership base. While the membership numbers are held secret, Warringah supporters have previously stated the NSW membership is as low as 8,000, though other Liberal sources say the numbers are closer to 12,000.

Bernardi has planned an event in Sydney next week and claims 4,000 paid-up AusCon members in NSW. He is also due to speak to the Roseville branch of the Liberal party next month.

Ruddick, also a conservative, won nearly 40% of the vote when he ran for NSW party president in 2012. He had been threatened with expulsion and suspension for speaking about party matters publicly, before he resigned his membership in 2015 when Turnbull became leader.

Ruddick was one of a number of conservatives who had lunch with Bernardi, the former Liberal senator, last month. They included another key preselection campaigner and conservative, Walter Villatora, who is also Tony Abbott’s federal electorate conference president. Abbott has argued for the change since he lost the leadership.

Even if the Warringah motion passes the convention, it has to go to the party’s constitutional committee, and also pass the party’s state executive, which is controlled by the moderate faction, which remains opposed to full plebiscites. Ruddick says he does not trust the party machinery to expedite the move to plebiscites.

“If Warringah only is approved we still have a battle ahead – the war of ratification,” Ruddick said. “The lobbyists are banking on bogging down ratification for years as they have done in the past. I can’t disclose strategy at this point … but I promise we will win the war of ratification within three months.”

The current preselection practice is that branches vote in local delegates, who vote for a candidate from a central pool. In some circumstances, the state executive can use special powers to intervene and change the rules to expedite the process.

NSW is one of only two states that does not have some form of plebiscite for preselection.

The NSW party state executive and its immediate past president, Trent Zimmerman, have long opposed plebiscites, arguing that the current system is appropriate because MPs are local representatives as well as flag bearers for the party.

On Friday, Zimmerman said all members should approach the convention prepared to compromise, which could mean support for either the Leeser or Hawke motions. But it is also possible that the convention could support two motions, such as the Warringah motion and one other compromise motion, if some members vote for both.

The convention is unprecedented in that any member could register to take part and vote. Electronic voting will be used, via smartphones, tablets or laptops, which had caused concern among some quarters of the party, given its ageing demographic.