Gary Humphries will stand again against Zed Seselja for preselection for the Liberals' top Senate spot if the ballot is held again.

Incumbent ACT Liberal senator Gary Humphries, left, and preselection challenger Zed Seselja. Photo: Colleen Petch

The result of the Canberra Liberals' Senate preselection vote looks certain to be challenged at an extraordinary general meeting of the party's ACT division next month.

Divisional president Tio Faulkner confirmed on Friday evening that a group of members had collected enough signatures to force a ''divisional council'' of all members to try to overturn the result and have the preselection held again.

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Party members will gather at the Eastlake Football Club in Kingston on Saturday morning to choose who will contest Canberra's federal seats in September's election - former ACT Liberals leader Zed Seselja or Senate incumbent Gary Humphries.

Voting day arrives with candidates still unsure of who is eligible to vote.

Mr Faulkner, who is backing the challenger, Mr Seselja, for the Senate spot, is now constitutionally bound to call the meeting no more than three weeks after receipt of the petition, which was delivered to the local party's Civic headquarters on Thursday afternoon.

The process was still mired in confusion and allegations of dirty tricks right up to the eleventh hour on Friday night. Even the right-to-vote of former deputy leader and party stalwart Brendan Smyth was in doubt with the validity of meetings of his southern electorate branch in Tuggeranong under a cloud.

Senator Humphries' office said on Friday evening that it still had not been supplied with an updated list of preselectors after many members were denied the right to vote on technical grounds.

The number of preselectors is now estimated at up to 217, from a total local party membership of about 640, but some claims put the numbers allowed to vote as low as 150.

A spokesman for Mr Seselja said he could not comment on Mr Smyth's voting status and the former leader declined to be interviewed on Friday.

The party's electoral returning officer, Martin Dunn, did not respond to requests for an interview on Friday.

Candidates for the lower house and upper house seats were supplied with lists of eligible preselectors, in keeping with party convention, early this month, soon after Mr Seselja declared his challenge to Senator Humphries, but fresh lists, reflecting the changes made in the intervening weeks, had still not been issued as The Canberra Times went to print on Friday.

Supporters of Senator Humphries and of dissident former president Gary Kent are expected to attend the football club, regardless of their eligibility to vote, to express their anger at the way the process has been handled.

Mr Kent, who is leading a push to have the preselection process overturned at the extraordinary general meeting, said the process had been divisive.

"If those who are disgruntled all rock up, there won't be room," Mr Kent said on Friday.

The bitter row that has engulfed the party has centred on branch meetings that members must attend within six months of the vote to qualify as preselectors.

But since Mr Seselja declared his candidacy, half an hour after the rolls closed, many of the meetings held by the party's local branches have been found to be not properly constituted, stripping attendees of their right to vote.

It is alleged that supporters of Mr Seselja were urged to attend two hastily convened meetings, of the Young Liberals and the Women's Council, just days before the former leader declared his challenge.

''Many members, including me, were not told about the meetings on time or at all,'' Mr Kent said.

''But Zed's supporters got their friends along and off they went, they qualified but I don't think those meetings were constitutional. It's deliberate strategy to make sure that as many of Zed's supporters as possible and as few of Gary's supporters were enrolled to vote.

''It's not the Liberal way, it's not the Robert Menzies way.''

The Senate preselection ballot is scheduled for 11.30am.