His call comes after long-term Canberra Liberals member and Belconnen businessman Ramon Montero says he left the party in disgust because he was unfairly denied the right to vote, as Mr Humphries and Zed Seselja prepare to face-off for preselection for the ACT senate seat.

Senator Humphries told ABC radio on Monday morning he believed Mr Montero was one of about 400 ACT Liberal party members who would be denied the right to vote, and said the preselection had become “unsustainable”.

“We should abandon this process. At least we should reopen the process long enough to allow qualifying meetings to be held in the various branches of the division,” Mr Humphries said.

To qualify to vote, a member must have attended a Liberal party meeting with a quorum in the six months leading up to the vote.

“The point is that Ramon and a number of other members of the party were advised that they were voting preselectors on the basis that at some point in the last six months they’d attended a meeting that apparently qualified them to be a preselector," he said.

“The information about their status was mishandled by the division.”

But party member and ACT MLA Vicki Dunne said while she was “deeply sympathetic” towards Mr Montero, the rules were long-standing, and she stood by the party’s preselection process.

“What we’re seeing now is the returning officer going through the roll and checking off to see if those meetings were valid, because the constitution says to be a voting member that you have had to attended a valid meeting, a quorate meeting in the last six months,” Ms Dunne told ABC radio.

“I would rather people miss out than there is any doubt about the validity of the preselection.”

The preselection vote is due to take place on February 23.