Changes that would allow three times as many Labor members to have their say on party preselections have been passed at ACT Labor's 2017 conference, after a motion to defer the proposal to a plebiscite was defeated.

The changes, championed by the party's left faction and voted up 128 to 72, would allow members vote on preselection without attending sub-branch meetings but have been criticised by the party's right as a way for the left to gain control of a possible third federal seat.

Before, party members would have to belong to a branch for at least 12 months and attend a certain number of meetings a year to be eligible to vote in preselection.

Now people will only have to belong for 12 months and be enrolled in the right electorate to vote for candidates.

ACT Labor secretary Matt Byrne said under the old rules, members with families or other commitments were considered "lesser members".

He pointed to low quotas for preselection for last election including 11 in Yerrabi and 19.1 in Murrumbidgee.

"Eleven people should not determine the future of 80,000 people's representation," Mr Byrne said.

Yerrabi MLA and member of the left faction Suzanne Orr said many of the volunteers who doorknocked for her could not vote for her as they had not gone to enough sub-branch meetings because of other commitments.

But Chris Sant from the Gungahlin sub-branch  said the changes left the preselection process open to interference, possibly for other political parties, as someone could sign up 20 to 30 members at a time. 

"This is the most branch-stacker friendly motion that we've seen at conference for a long time," Mr Sant said.

Mr Byrne told Fairfax Media he believed existing rules, which limited the number of new members at one branch to eight a month, were strong enough to stop any undue influence on the preselection process.

Right faction member and former ACT politician John Hargreaves said "if it ain't broke don't fix it". 

"If it's broke that means then we really did the wrong thing by preselecting all the people in the front row here. We blew that did we?" Mr Hargreaves said.

"I've spent all of my life in the party and I don't want to see it go down the toilet."

Shane Carter , a nurse an a father of three, said if he could find time to attend branch meetings around his shifts anyone could.

"It's not that goddamn hard," Mr Carter said. 

Karl Maftoum called for the changes to be referred to a select committee and to be voted on via a plebiscite of the entire ACT branch. His motion was defeated. 

About 224 delegates attended the annual conference on Saturday.

In his address, Chief Minister Andrew Barr vowed to back federal Labor leader Bill Shorton's push for a referendum on Australia becoming a republic. 

He also announced an extra $3 million would be invested in the Belconnen town centre, Labor heartland. 

Former Labor Kate Lundy was made a life member of the ACT Labor branch, as was former MLA Jayson Hinder who died in a motorcycle accident earlier this year.  

Liz Boyle, Declan King and Bill Thompson were also named life members. 

An earlier version of this article said a quota for Murrumbidgee was 13.