After 12 years in coalition, the Greens will not serve in the next ACT government, but will continue to support Labor from the cross bench.

The party – with four members in the Assembly – will hold the balance of power from the cross bench, which will also include two new independent members.

Leader and former long-time cabinet minister Shane Rattenbury said negotiations with ACT Labor had not delivered enough of a commitment to address the issues of climate change and public housing “in order to give us confidence that any power-sharing agreement would deliver the level of change that Canberra needs”.

Rattenbury said he wrote to the Chief Minister late on Tuesday night asking for his support to commit to a number of key Greens policies in exchange for confidence and supply, and support for Andrew Barr as chief minister. The details of these policies would be announced in the coming days.

“Negotiations were unable to produce a commitment from Labor to build enough public homes that people on low incomes can afford, tackle our transport emissions, or increase the government’s ambition on restoring our environment,” he said.

“The ACT Greens did not demand an exact commitment to our policies – negotiation requires compromise and we offered compromise. But on some of the most important matters to our party, Labor was unwilling to budge.

“In housing, ACT Labor was not prepared to commit to a single extra public home beyond their existing policy.

“On climate, we know that transport is responsible for 60 per cent of our emissions, but Labor was not willing to accelerate building light rail or invest properly in active travel.

“On the environment, they were not willing to commit to any specific funding which would scale-up our ambition on environmental protection and restoration.

“These are key priorities that the ACT Greens made clear were essential to securing our support during the election, including a commitment to build 10,000 new public homes, build light rail faster and establish a $50 million Bush Capital Restoration and commit $50 million towards healthy waterways.

“If we truly accept that the housing market is in crisis, and if we truly accept that our climate is in crisis, then we cannot in good conscience continue to deliver a business-as-usual approach to government when people and our planet are hurting.

“As a party we have made this decision not in an effort to block progress that Labor is willing to agree to, but to use the position Canberrans put us in at the election to contribute to a positive public conversation about the bolder change that is needed for our city.

“By sitting on the crossbench during this term of government, we are confident we are using the best mechanism available to us to push for bolder change and create a better deal for Canberrans – to build public housing, go further, faster on our nation-leading climate action and truly protect and restore our environment.”