In the review, Scales has described the ALP's decision to establish NBN Co as one that was "rushed, chaotic and inadequate".
Scales was appointed by the coalition government in March to conduct the independent audit.
Rather than giving a large, well establish telecommunications company the task of taking on the $43 million project in the given time frame, the government created NBN Co that was clearly "not fit for purpose", according to the review.
"Meeting the government's very tight time frames for the rollout of its NBN program would have been a significant challenge, even for a well-functioning, large and well established telecommunications provider. For a start-up, it was an impossible assignment," the review said.
"The government decided to establish a completely new start-up public company, something that was extremely rare at the commonwealth level, to roll out one of Australia's largest ever public infrastructure projects, in eight years, at a cost still to be determined, but estimated at around $43bn, without a business case or a cost-benefit analysis, without clear operating instructions."
The review recommended large public-sector projects costing more than $1 billion be subject to rigorous cost benefits analysis, the results of which should be made public prior to commencement.
Political response
Minister for Communications Malcolm Turnbull condoned the analysis proposal as being "a very good argument", particularly pertinent to the NBN which was "an extraordinarily leap into the unknown".
"It was just a ramshackle, reckless excursion which has cost the nation tens of billions of dollars," he told reporters.
Responding to the review's scathing criticism of the network he was responsible for setting up, Labor Senator Stephen Conroy slammed Turnbull's move as one of a series of "political attacks" that was costing the public pocket.
"Why is Malcolm Turnbull spending $10 million of taxpayers' money to attack the NBN? Because his policy is a dog," he said.
"He's failed to meet his own election commitment where he said he'd get 90 per cent of Australians with 25 meg speeds by 2016 – already abandoned."
He also attributed blame to construction companies who were hired but "failed to deliver" on conditions made in their contracts.
"That was where we optimistically believed that construction companies would deliver," Conroy said.
