Within minutes of the Australian Electoral Commission's announcement of a third lower house seat for the ACT, Mr Barr said he would not be standing for Labor.

"I am enjoying my current role and there is much still to do. I won't be seeking pre-selection for the next federal election," Mr Barr told The Canberra Times.

Along with federal colleagues Gai Brodtmann and Andrew Leigh, Mr Barr welcomed the ACT's larger presence in the expanded House of Representatives, just a year after the ACT's Legislative Assembly grew from 17 to 25 members.

"Increased ACT representation in the federal Parliament is appropriate given our population growth – the ACT deserves more representation on national issues," Mr Barr said.

"Canberra is growing quickly and people are moving here faster than ever before for our high standard of living and high quality jobs, healthcare and education services."

Ms Brodtmann, whose seat of Canberra has the largest population in the country, said she was "delighted" by the commission's announcement.

"Any fair, democratic system should be as close as possible to one vote, one value. By that measure, the ACT is currently grossly under represented," she said.

Dr Leigh said he would "never say no to more representation for Canberra, particularly if that means another voice supporting equality, multiculturalism and the fair go."

While Mr Barr is one of the more experienced hands in the Legislative Assembly, he has only won one election as Chief Minister, and there are few experienced contenders likely to succeed him, despite speculation circling ministers Meegan Fitzharris and Yvette Berry.

A number ACT Labor branch members are also understood to be considering their options, despite the fact the candidacy of unsuccessful candidates in the last territory elections could be hampered, in the unlikely event a recently-elected ACT MLA decides to run.

Candidates who did not get across the line last year could gain an Assembly seat in the event of a casual vacancy.

This is especially pertinent in the case of Yerrabi - where three of the five Labor candidates got elected and one has since died, leaving only Deepak-Raj Gupta to fill the seat should Meegan Fitzharris, Suzanne Orr or Michael Pettersson step down.

It is also relevant in the electorate of Brindabella, where Angie Drake or Karl Maftoum could be called up if Mick Gentleman or Joy Burch retired from politics this term.

ACT Labor secretary Matt Byrne said it was still "early days" and nothing would be clear until the new boundaries had been declared, a process which can take upwards of a year.

ACT Greens convenor Michael Mazengarb said the party saw a new seat based around central Canberra as "a potentially winnable seat", and the party would look to replicate its success with Adam Bandt in the federal seat of Melbourne.