Treasurer Stephen Mullighan refuses to rule out scrapping tunnels from Torrens-to-Darlington design

Treasurer Stephen Mullighan has refused to rule out a major overhaul of the trouble-plagued Torrens-to-Darlington project – with the twin tunnels possibly cut.

Treasurer Stephen Mullighan has refused to rule out a radical overhaul of plans for the plagued Torrens to Darlington project, which would see the twin tunnels scrapped from the design.

It comes as confusion reigns over the funding deal for the final stage of the North-South Corridor, with revelations the federal government has delayed spending more than $700m on the project over the next four years.

This is despite Prime Minister Anthony Albanese’s government insisting it has kept the funding levels the same at $2.3bn over the forward estimates – up to an including 2025-26.

As the state government forges ahead with property acquisitions and demolition along the corridor, Mr Mullighan said he could not rule out major changes to the 10.5km reference design.

“We haven’t got any advice back from (the Transport Department) yet, not even informally, about what they’re looking at doing,” he said.

Mr Mullighan said it was the government’s “very strong preference” to deliver the tunnels within the $9.9bn already budgeted – adding the Transport Department’s review would not be finalised until the end of the year.

A concept image of the southern portal of the northern tunnels, South Road, part of the Torrens to Darlington project. Supplied: SA Government

Last week, Mr Mullighan warned the state would struggle to complete construction unless the federal government stepped in to cover a potential blowout, maintaining its 50:50 funding commitment.

Labor’s first federal budget in more than a decade revealed $730m for “nationally significant” road investments had been pulled from SA over the next four years.

SA Transport Minister Tom Koutsantonis explained the federal government had altered its spending to match the state government’s “reprofiling” of the Torrens to Darlington in its May budget – pushing out the construction start date by a year to 2024.

“The advice I have received from the department is that’s just a reprofiling of the North-South Corridor money,” Mr Koutsantonis said.

“That’s all that is.”

But in a major paradox, officials from both the Infrastructure Department and the Prime Minister's office told The Advertiser the funding had not changed since the Coalition’s March budget of $2.3bn over the next four years.

There was no mention of the Torrens to Darlington in official budget papers released on Tuesday – indicating the spending level for the project had not changed since March.

The federal government has saved $6.5bn by “deferring infrastructure spending” across the country “to not compound supply constraints or to better assess their merits”.

Treasurer Stephen Mullighan. Picture: Sarah Reed/Getty Images

Budget papers unveiled on Tuesday night showed Labor has maintained its original funding commitment of $4.9bn, despite latest cost projections running as high as $14bn.

Mr Mullighan said the state government had not yet asked its federal counterparts for more money because a Transport Department review was still ongoing.

Results of the review recently published on the department’s website indicated the tunnels would remain in the reference design, but the government insists the “draft” site contained inaccuracies and did not constitute any final recommendations.

Official results are due to be released by the end of the year.

Mr Mullighan said it was the government’s “very strong preference” to deliver the tunnels within the $9.9bn already budgeted.

“If the tunnels end up being more expensive then our first thoughts will be, ‘well, how much more expensive and can we afford it?’,” he said.

“Because, from the outset, our preference is to deliver the tunnels and we haven’t considered changing course on that at this point in time.”

Last week, Mr Mullighan warned the state would struggle to complete construction unless the federal government stepped in to cover a potential blowout, maintaining its 50:50 funding commitment.

The start of construction on the project has been pushed back from 2024 to 2025, and the completion date has been pushed back a year to 2032.

Opposition treasury spokesman Matt Cowdrey said the budget cast further doubt on the future of the project

“This budget was a prime opportunity for certainty over the North-South Corridor project but it’s achieved the exact opposite, with huge questions looming over who will cough up the billions needed for its completion,” he said.