The ACT government did not spend almost $250 million that had been set aside for construction and infrastructure projects last financial year.
While the government said it would spend $767 million on capital works in 2019-20, the audited budget papers showed the final figure was only $521 million.
Chief Minister Andrew Barr has attributed the significant underspend to a slower-than-anticipated delivery of infrastructure projects.
The government has also fallen behind its building program this financial year, having spent just 35 per cent of total available capital works funds for the year by December.
Transport Canberra and City Services had the largest chunk of funds available for this financial year, but spent only 22 per cent of it - about $50 million - in the first six months.
Construction was yet to begin on some of the biggest projects in the ACT's infrastructure plan.
They include the long-delayed major expansion of Canberra Hospital (first promised in 2016), CIT Woden redevelopment, and light rail stage 2A.
Mr Barr has conceded the government's ambitious infrastructure agenda was also unlikely to be fully met this financial year.
A government spokeswoman said there were multiple reasons last year's targets were not met.
"COVID-19 was the single largest and had a significant impact on the delivery of capital projects," she said.
"Other factors included wet weather, extreme weather events (eg bushfires, hailstorms), defect periods for projects resulting in financial completion of a project lagging physical completion by 3-12 months, and in a small number of cases ongoing planning approval processes delaying commencement."
She said the government prioritised smaller projects that were ready to progress quickly in order to protect jobs during the pandemic.
"Access to skilled workforce and certain construction materials has been a problem faced not just in the ACT but around Australia, and this will continue to impact on the ability to progress quickly with major infrastructure projects," she said.
"Noting these trends, the government will look to adjust some financial aspects of capital works program between the forward years in the next annual Budget round."
Opposition leader Elizabeth Lee said Mr Barr had not been up front about the public before polling day last year.
"Since the election, the chief minister has continually raised concerns about his government's ability to deliver the infrastructure projects it promised Canberrans," she said.
"The government's latest underspend on infrastructure is just another example of its broken promises."
She said Mr Barr "must come clean" about which projects and election promises would be delayed or not delivered.
"If this is what we are seeing from the Labor-Greens government just five months after an election, every Canberran has the right to be seriously concerned about what this means for our city over the next three-and-a-half years," Ms Lee said.
Master Builders ACT chief executive Michael Hopkins welcomed the government's increased allocation of funds to infrastructure projects.
"The feedback from our members is that the opportunity to tender with the ACT government is certainly increasing," he said.
"Lots of the local projects the government have been tendering have been awarded to local contractors."
But Mr Hopkins said there was plenty of capacity to scale up work in the local industry.
"In 2018 there was a spike in the level of infrastructure that was delivered," he said.
"There's no reason we can't deliver to the levels of 2018 going forward. Over the medium term and longer terms we should be investing in skills and education so we're creating more local capacity."
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