The bitter ACT Liberal preselection fight between Zed Seselja and Senator Gary Humphries is set to continue even after a candidate is selected this weekend.

A meeting of party members in two weeks will be asked to overturn the controversial preselection process.

Senator Humphries says the preselection process is being rushed to favour his opponent, prompting former party president Gary Kent to this afternoon submit a petition of more than 90 members, calling for a meeting to overturn the weekend's vote.

Under the party's rules that vote must be held between two and three weeks from today.

Mr Seselja stood down as Territory Opposition Leader to challenge Senator Gary Humphries for the number one spot on the party's ACT Senate ticket.

"They're free to do that and I encourage them to do so," he said.

"I'm confident that once a decision is made, that even if there is a process to go through, the party will get behind that individual."

Both Mr Seselja and Senator Humphries acknowledge the result will come down to a handful of votes.

All the Liberal members in the ACT Legislative Assembly have written an open letter to party members urging them to support their colleague Zed Seselja.

Senator Humphries says it was probably written out of a sense of duty.

Senator Humphries already has the support of Federal Opposition Leader Tony Abbott.

"My colleagues in the Federal Parliament appear to be equally united they want me to stay where I am, and Zed to stay where he is," he said.

"I would rather have that endorsement frankly than the endorsement of MLA's."