The Opposition has referred the ship lift project for investigation by a parliamentary committee after massive costs blow-outs and last week’s announcement that the lead contractor has entered administration, raising further questions about the ongoing viability of the project.

Deputy CLP Leader Gerard Maley said he was concerned that the ship lift had started with a $100 million price-tag six years ago when the CLP were still in power and was last costed at $515 million earlier this year.

The new figure was $115 million more than previously disclosed, with the government blaming an unexpected increase in construction costs.

“There has been no business case made public by the Fyles Labor government, and Territorians have been left in the dark as to whether this project will provide value for money,” Mr Maley said.

“Just last week, one of the two participants in the construction joint venture, Clough Group, entered administration, adding uncertainty and potentially meaning additional costs will be incurred by the Territory.

“Territorians deserve to know if this project will return a profit, including whether the cost of the project will generate return on investment within a reasonable amount of time.”

Mr Maley said he referred the ship lift project to the Public Accounts Committee for investigation and expected the parliamentary body chaired by Labor backbencher Joel Bowden would agree to reviewing the matter before Christmas.

“It is in the interests of Territorians that this committee put this project under the microscope, especially as the Territory heads to a $10 billion debt by 2026,” he said.

The Auditor General previously found in 2018 that the earlier $100 million government pledge by the then-CLP government for the project was not based on any economic modelling and that the government did not complete a cost-benefit analysis.

However, an early pre-feasibility report considering the direct economic benefits of what was then proposed as a larger “marine maintenance precinct” found it would return just 65 cents for every dollar spent, but the rest of the project has since been scrapped and will now only be a ship lift facility, which the government has not been able to provide any modelling that shows it will be feasible.

Last week it was revealed that Clough – the major company awarded the contract to build the ship lift in a joint venture with BMD Group in May – was placed in voluntary administration after a merger fell through.

The funding model will see Territory taxpayers shell out more than $200 million for the project, with the other $300 million in the form of a concessional loan from the federal Northern Australian Infrastructure Facility (NAIF).

Paspaley is not contributing any money to the project but will operate the facility for profit.

The government has said the ship lift would be capable of servicing large vessels of up to 5,000 tonnes and will “be used for multiple industries including offshore petroleum, fishing, pearling and Defence and Border Force”, but neither the ADF nor Border Force has committed to using the facility.

The government also vaguely claimed without providing any evidence that the ship lift would “bring millions into the NT economy every year” and would employ 250 Territorians during the peak of construction, as well as “generate and maintain hundreds of local jobs in the maritime support sector”.

Clough and BMD had finally commenced work on the project in September.

Chief Minister Natasha Fyles said the government was “working through” what the collapse of Clough meant for the project.

“But we’re just working through what this means in terms of the administration and sometimes companies can trade their way out of administration,” Ms Fyles told the NT News.

“I don’t know the specifics of this but we’re certainly working through everything.

“This went through a very strict due diligence process and I’ve got no reason to have any uncertainty around that.”

The Darwin ship lift was expected to be operational by the end of 2024, but it was still unclear what impact the collapse of Clough will have on that timeframe.