Vanessa Picker, an Independents for Canberra candidate in the southern seat of Brindabella, says she would not support Andrew Barr to stay as chief minister.
But Dr Picker said her statement did not imply any commitment to support a particular party if she held the balance of power.
"I refuse to make such a commitment prior to the election, as doing so would severely compromise my independence and my ability to respond to the evolving needs and views of our community," Dr Picker said in a statement posted to social media on Saturday.
"However, I unequivocally stand by my call for a new chief minister."
Dr Picker called on her fellow independent candidates to join her public commitment not to support Mr Barr's leadership of any future ACT government.
"The people of the ACT deserve a chief minister who truly listens, understands their concerns, and takes decisive, meaningful action," she said.
"For nearly a decade as chief minister - and close to 20 years as an MLA - Mr Barr has utterly failed Tuggeranong and its surrounding communities, turning a blind eye to the stories of neglect and harm in our electorate."
Independents for Canberra leader and co-founder Thomas Emerson said he did not share Dr Picker's position and remained open to all options.
"If Independents for Canberra MLAs hold the balance of power after the election, we will negotiate in good faith on behalf of our communities. We will follow our shared principles in seeking agreement on whom to support as chief minister," Mr Emerson said.
Mr Emerson said candidates elected under the Independents for Canberra banner would take into consideration any prospective chief minister's willingness to collaborate with the crossbench and support its policy positions.
"There is, however, no mechanism within our organisation to demand that any of us as independent candidates do anything except demonstrate commitment to the principles we all agreed to at the outset," he said.
"Those principles include collaborating while remaining free to disagree, ensuring every voice is heard, acting with integrity, and grounding policy in evidence."
Independents for Canberra this month said whoever was chief minister should not also be the territory's treasurer. Mr Barr has long held both portfolios.
Dr Picker on Saturday accused Mr Barr of using "last-minute, hollow gestures and promises" and of "brazenly admitting that these actions are motivated by his desire for Labor to reclaim the seat narrowly lost in the last election".
"This is not the conduct of a leader who genuinely cares about the people he serves; it's the behaviour of someone clinging to power," she said.
"Accountability should not be confined to the ballot box every four years. I'm hearing from my community, loud and clear, that Mr Barr should not even have the privilege of leading Labor into the next election."
Mr Barr in January issued a veiled warning to voters to be wary of "stooge independents" running for the Legislative Assembly at the October election.
Mr Barr, who became the longest serving chief minister this year, said independent candidates would not presumably seek to form government in their own right, which meant they needed to decide who they would support.
"So that's a question I think they should answer before polling day and give a straight and honest answer to the community," Mr Barr said.
"Are they running as an independent to support a Liberal government, or would they support a Labor government?"
Mr Barr said at the time he anticipated a fierce competition for the Assembly's crossbench, but said Labor had shown its capacity to work with other members to form government.
"In the past, we've worked with Democrats, we've worked with independents, we've worked with the Greens. So I think the key and consistent theme in that is our ability to work with others," he said.
The election for the 25-member Legislative Assembly will be held on October 19.
