The Independents for Canberra party says the ACT's chief minister and treasurer should not be the same person, pledging to try to prevent this if they hold the balance of power after the October poll.
The group said allowing the chief minister to hold the treasury portfolio threatened the integrity of democracy.
Andrew Barr has been the ACT Treasurer since 2011. He became the Chief Minister nearly 10 years ago and has retained the treasury portfolio throughout the time.
Independents for Canberra leader Thomas Emerson said this created a situation where there was little opportunity to challenge Mr Barr.
"Democracy thrives on dynamic tension," Mr Emerson said.
"It is well known that very little happens in the ACT without the say-so of our current Chief Minister, who is also the Treasurer.
"Other Labor-Greens ministers seem to have little capacity to challenge 'the Chief'."
Mr Emerson pointed to a recent example where Environment Minister Rebecca Vassarotti, who is in the Greens, hit out at Labor for not going further in its response to recommendations for a report to protect the environment.
Ms Vassarotti told the Assembly in June: "While I present the government response, this is only as far as the Labor majority government was prepared to go".
Following the 2020 election, Mr Barr said he would hand over the Treasury portfolio during this parliamentary term but he has since backtracked on this.
"There will be a handover and it's just a case of whether that is in 2022 or 2023 [and it] will depend on where we are with the economic recovery," he told The Canberra Times in November 2020.
Under the Self-Government Act, administrative arrangements for ministers are determined by the Chief Minister.
An ACT Labor spokeswoman said every chief minister since self-government had held the Treasury portfolio for some or all of their time in office.
The spokeswoman said it was not uncommon for leaders in smaller parliaments to also be the treasurer. She pointed to several examples in the Northern Territory, including current NT Chief Minister Eva Lawler, Tasmania and South Australia.
The current ACT cabinet has nine members and the three most senior members are part of an economic review committee. The members are Mr Barr, Deputy Chief Minister Yvette Berry and Attorney-General Shane Rattenbury.
"The Expenditure Review Committee make recommendations to the full Cabinet. Budget decisions are made by the full cabinet," the spokeswoman said.
"Our focus is delivering a positive plan for Canberra's future, and not on horse trading future administrative arrangements and ministerial responsibilities."
Opposition Leader Elizabeth Lee is also the shadow treasurer.
Mr Emerson said the Assembly needed more checks and balances.
"Lacking an upper house, the ACT's unicameral parliamentary system is set up for a minority government, where genuine negotiation and ongoing compromise are commonplace," he said.
"That's been thwarted by Labor and the Greens working as a coalition."
One minor party contesting the election has rubbished the Independents for Canberra position. Belco Party co-convenors Jason Taylor and Bill Stefaniak said they did not believe it was up to the cross bench to determine who holds a portfolio.
"It is the decision of the Chief Minister as to who makes up their cabinet, and what portfolio they hold. By all means criticise Mr Barr for yet another broken promise for failing to transition the Treasury portfolio to somebody else, but it is not a vehicle to tell the electorate you will decide who can hold certain portfolio's," the pair said.
"That is not independent, it's seeking to be a king maker, and is not a position we will support."
