The ACT Greens have ruled out forming government with the Canberra Liberals, saying the party was too blatantly populist and lacks conviction to tackle tough issues.
Greens leader Shane Rattenbury confirmed his party, which governed in coalition with ACT Labor in the last term, would not work in a similar arrangement with the Liberals.
To form government, the Liberals would need to win an outright majority of seats, a feat which only Labor under former chief minister Jon Stanhope has managed, or secure the support of a right-leaning independent or minor party member.
Writing in an opinion piece for the Sunday Canberra Times, Mr Rattenbury said Liberals leader Alistair Coe was one of the country's most conservative politicians.
"We're in a climate emergency. At a time when urgent action, not climate scepticism, is required of politicians, we need people with real conviction and a willingness to tackle the tough issues, not people whose first instinct is to blatant populism. Alistair Coe's Liberals simply don't meet that standard," Mr Rattenbury wrote.
"At this point in our history, the Greens understand that we must treat the climate crisis, the housing crisis and the jobs crisis with the same boldness and decisiveness as we have the COVID-19 crisis."
Mr Rattenbury, who has sat in cabinet since 2012 following a landmark agreement struck with then Labor leader Katy Gallagher, said the two-party government was "imperfect" but Greens party policies were still enacted in the last term. A new agreement was made following the 2016 election.
"We have worked hard to ensure that for Canberrans, who expect a progressive, sustainable and inclusive Canberra, [the two-party government] has delivered," Mr Rattenbury said.
Earlier this month, Mr Rattenbury left open the possibility of forming government with the Liberals, should the opportunity present itself.
"We don't presume to get that far ahead of ourselves - we need to see the outcome on polling day," he said at the time. "We hope to have enough seats to play a role in the government going forward.
"Our members will play a really big part in that discussion as well. We will have discussions with members both before and after the election on what they want to see their parliamentary representatives do."
Mr Coe said at the time it was "highly unlikely" the Greens would support the Liberals.
Only the Labor party under Mr Stanhope has commanded an outright majority in the Legislative Assembly, between 2004 and 2008. The Liberals would likely need to win 13 seats at the October 17 election to form government.
The 2016 parliamentary agreement between Labor and the Greens committed the Greens to supporting Andrew Barr as Chief Minister, guaranteeing supply and not moving or supporting no-confidence motions except in instances of corruption, negligence or significant non-adherence to the agreement.
One-fifth of the proposals in the agreement went undelivered, but 89 items were completed, including banning donations from property developers to political parties and funding extra school psychologists.
After the 2012 election which saw three Greens members lose their seats, Mr Rattenbury entered into talks with Labor leader Katy Gallagher and Liberal leader Zed Seselja.
It took nearly two weeks from election day for Mr Rattenbury to reach an agreement with Labor to form government, but party members at the time were understood to have expressed support for a deal with the Liberals in an effort to take back the Greens' identity.
Mr Rattenbury all but ruled out working with the Liberal party before the 2016 election, citing irreconcilable differences between the parties' light rail policies.