Senator Humphries and his supporters have accused the party's management committee of rorting the preselection process to favour his challenger, ACT Opposition Leader Zed Seselja.
Mr Seselja announced on Monday that he will be challenging Senator Humphries for his safe Liberal seat.
Senator Humphries says the process has been rushed so his supporters will not be able to fulfil the requirements to be eligible to vote in the selection process on February 23.
The party's leadership held an emergency meeting last night to discuss the concerns, but decided not to change the timetable for preselection to allow more members the option of voting.
Senator Humphries says he is not happy with the decision.
He says only a third of the party membership are signed up to be preselectors.
"As a result I think the electoral college is far too small," he said.
"We need to make sure that every member of the division who is financial has the opportunity to vote and that hasn't been facilitated I gather by the decision made last night."
Senator Humphries says he is exploring other options to encourage the management committee to change the preselection timeline.
But the management committee has defended its handling of the preselection process.
In a statement the party executive says that it is sticking by its original timetable and will not be extending the time period in which party members can qualify to vote in the preselection poll.