The ACT's seven ministers are stretched across 31 portfolios, with deputy chief minister Yvette Berry holding six and disability minister Rachel Stephen-Smith holding five.

Mr Barr on Monday called for expressions of interest from his backbench, which includes former early childhood sector lobbyist Chris Steel, ex-hairdresser Bec Cody, former CFMEU organiser Michael Pettersson, ex-public servant and voluntary euthanasia campaigner Tara Cheyne, and town planner Suzanne Orr.

He will select the new minister later in the week, although it is unclear at this stage which portfolios they will pick up.

"Canberra is now a city of 420,000 people. Our population is projected to reach half-a-million people in the next decade," Mr Barr said in a statement.

"In response to our city’s growth, and to achieve our plan for the territory, we will be expanding our ministry team. A new minister will allow new priorities to be delivered, resulting in better outcomes for Canberrans."

A backbencher earns $164,382 while a minister earns $279,450.

However, Mr Barr said the ACT would continue to have "the smallest executives of all the states and territories".

Both the Tasmanian and Northern Territory parliament have nine ministers, although there are 24 portfolios in the Northern Territory government and 34 in the Tasmanian government.

The cabinet last expanded to seven members when the Legislative Assembly went from 13 to 25 members in 2016.

Mr Barr hinted to the cabinet expansion in question time last Tuesday.

Canberra Liberals deputy leader Nicole Lawder asked if Mr Barr still had confidence in Health, High Education and Transport Minister Meegan Fitzharris after a "litany of failures" under her watch.

"Yes, very strong confidence," Mr Barr said.

The Liberals' health spokeswoman Vicki Dunne asked if Mr Barr would reduce the workload of Ms Fitzharris "so that she can get at least something done right".

"Of course I am constantly looking at issues of workload across territory government and this is something that has been brought to my attention not just by your question, Mrs Dunne, but indeed through conversation with colleagues and looking at the government’s forward priorities," Mr Barr said.

"It does of course remain within the purview of the Chief Minister to undertake consideration of the administrative orders and of course I can do that at any time. I take these matters seriously. Minister Fitzharris continues to do an outstanding job in each of those portfolio areas and as I indicated in my response to the first two questions Minister Fitzharris retains my confidence, the confidence of all her colleagues and the confidence of the people of the ACT."

Andrew Barr

Yvette Berry

Meegan Fitzharris

Mick Gentleman

Gordon Ramsay

Shane Rattenbury

Rachel Stephen-Smith