The cost of Australia's largest rail project has doubled to an "astonishing" $31.4 billion and is riddled with problems such as major delays, environmental challenges and inexperienced project managers.
An independent review into the Inland Rail, which links Melbourne and Brisbane to take freight off roads, has found the project faces "serious problems" and some work should stop to get costs under control.
Report author Kerry Schott said construction began "somewhat surprisingly", without knowing where the route would start or finish.
"The detailed and clearly defined scope of much of the route has not yet been settled as approval processes are not complete," Dr Schott wrote in the report, due to be made public on Thursday morning.
"Until this scope is firmed, an assessment of schedule and cost cannot be made with confidence."
The coalition government in 2015 said the project would cost $10.7 billion, then $16.4 billion in 2020 and the railway was expected to operate from 2027.
The latest estimate by the government-owned Australian Rail Track Corporation, which manages the Inland Rail, was $31.4 billion with completion expected in the early 2030s.
Dr Schott said that proposed schedule should be regarded with "great caution", particularly as the corporation's poor environmental impact statements had not been approved by the Queensland government.
The rail track corporation's board had "weak" expertise in engineering, safety, environment and sustainability and contracts, something its members raised with coalition government ministers responsible for board appointments, she said.
"Across the entire project, ARTC has pressed ahead trying to make a virtually impossible delivery time, possibly pressed upon them by previous governments," Dr Schott wrote, urging it to stop work and spending on delayed parts of the project.
Dr Schott made several recommendations, including that Inland Rail be made a subsidiary company to allow it greater control of project management and the approvals process.
The project should also focus on being competitive with road transport, offering a 24-hour transit between the two cities, while further independent assessments of costs and scope were needed.
Despite its complex problems, the government should not abandon the project, she said.
"As it stands, Inland Rail is expected to accommodate and drive a modal shift of 200,000 trucks a year to rail, and this will bring significant benefits in terms of supply chain efficiencies, safety, environmental and congestion reductions."
Infrastructure Minister Catherine King said the report revealed the coalition government's "shameful" approach.
"They have let down communities and businesses which have already invested time, effort and money in the prospect of Inland Rail," Ms King said.
"It is now up to the Albanese government to clean up this latest mess and we will do so in a prudent and responsible way."
