Ms Morgan had nominated for preselection in the seat of Bean after the shock resignation of MP Gai Brodtmann, but was originally found ineligible because one of the three branch meetings she had attended was found inquorate.

She was reinstated by a special motion at the party's annual conference on Saturday, supported by unaligned members and the left faction, despite identifying with the right.

The push to have that decision overturned at a national level came from powerful unions within the right faction, seen as a move to shore up votes for Senator David Smith, who has put his hand up for the seat instead of facing a Senate preselection battle against Katy Gallagher.

Accordingly the vote was also made along factional levels, with the 11 votes on the national executive controlled by right factions out-numbering the 10 associated with the left.

The motion from the conference was disallowed, with the executive noting it left the party open to adverse action against it by other candidates or party members.

ACT Labor secretary Matt Byrne didn't comment on the decision today, except to confirm the final three candidates for Bean were Senator Smith, staffer Taimus Werner-Gibbings and public servant Louise Crossman.

It means just woman will appear on the ballot for each contested preselection, with Alicia Payne the only woman running to represent the party in Canberra.

Women in the party's right were discouraged from running against Senator Smith at preselection before he was endorsed by the party's right faction.

Internal polls within the party open on Saturday, with voting continuing on Wednesday and Saturday September 1.

Ms Morgan wished the other candidates well in a statement.

"Obviously I'm disappointed by the decision of the national executive. I wish all the candidates the best of luck and I will be out there every day fighting for a Shorten Labor government," Ms Morgan said.

Meanwhile, the left's star candidate for preselection in Canberra John Falzon announced this week he had resigned from his job as chief executive of the St Vincent de Paul Society on Monday to focus on the party process.

Mr Falzon and Senator Smith are seen as the most likely candidates to win each preselection, with shadow assistant treasurer Andrew Leigh to represent the party in Fenner. This would mean the party would fail to meet its affirmative action rules encouraging more women to nominate for public office.

But with the prospect of a looming election, all branches are facing pressure to wrap up their preselection processes quickly and face the increasing likelihood the party's national executive will step in to decide candidates.