Inland Rail is a 1700km line intended to link the capitals via a route through regional Victoria, NSW and Queensland to take freight off roads.

But an independent review said the project 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,” report author Dr Kerry Schott wrote.

“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.

Schott said the section between Melbourne and Parkes could be completed by 2027, but there was no indication of the timing of the project beyond this.

While progress was being made in terms of NSW approval processes, Queensland’s work was “well behind” with Schott saying she would not “hang her hat” on the 2030s estimate for the Queensland leg of the project.

She 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,” Schott wrote, urging it to stop work and spending on delayed parts of the project.

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.”

Transport Minister Catherine King said it would take a lot of work to get the project back on track.

“The previous government began this project with no idea where the rail line would start in Melbourne, and where it would finish in Brisbane, or how it would interact with towns, communities and the natural environmental along the route,” she said.

-with AAP