The government agreed to just one of 12 recommendations from the Commissioner for Sustainability and the Environment, designed to reduce scope-3 emissions, in addition to scope-1 and 2.

Commissioner, Sophie Lewis, said the shortcomings in the response extended beyond not setting scope-3 targets, which result from the production of goods imported into the ACT.

"What I see is, 'that's too hard, we're focusing on scope 1'," Dr Lewis said.

"I had really hoped to see more ambition and more commitment to reducing greenhouse-gas emissions for the territory."

The recommendations came from a government-commissioned report identifying several ways to reduce scope-3, which also provided tested methodology to measure emissions.

The report found scope-3 emissions made up 94 per cent of greenhouse gas emissions generated by the ACT, with government responsible for 33 per cent of scope 3.

Dr Lewis said several achievable changes recommended by her office would make a huge impact in reducing the territory's overall footprint.

"We've got 12 recommendations and some of those were really hard to achieve - this is a hard thing to do," Dr Lewis said.

"But seeing that only one of those recommendations was agreed to is really disappointing."

Minister for Emissions Reduction Shane Rattenbury said the current priority was to reduce scope-1 emissions, through transitioning away from fossil-fuel gas and cutting transport emissions.

He said the legislated emissions reduction targets, scope 1 and scope 2, were consistent with international greenhouse-gas emissions protocols, designed to avoid double counting.

"Before we can address our scope-3 emissions and set targets, it is important that we develop a way to measure and report these emissions," Minister Rattenbury said.

"Estimating and reporting scope-3 emissions from all sectors across the territory is a complex task, but our methodologies have been improved over time and will continue to be refined as new information emerges, and as international practice improves."

Targets to reduce scope-3 emissions received support from the government's standing committee on environment, climate change and biodiversity.

"For the ACT to reach its goal of net-zero by 2045, targets for all emissions need to be set," the committee reported during annual reports hearings.

"Future emissions reporting by the government should include scope-3 emissions."

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Dr Lewis said choosing not to determine opportunities to increase low-carbon cement supply in the ACT was a missed opportunity.

"There's construction - for residential for commercial - everywhere in Canberra is being built right now," Dr Lewis said.

"This is a place where we can lead that innovation in terms of how we're designing our buildings and the materials that we're using.

Dr Lewis said any changes made in the scope-3 realm was going to have huge positive impacts on the environment.

"It's great that we're working on scope 1 in the ACT, but to say that 'we're already doing that, we're busy doing that, so we can't look at scope 3' to me is really disappointing," Dr Lewis said.