Sydney Metro under review amid $20b budget blowout

A flagship rail project sending driverless trains under Sydney Harbour and the city's west will undergo a major review after cost blowouts topped $20 billion.

The second stage of Australia's first fully automated rapid transit system, the Sydney Metro City and Southwest project, is on track to cost at least $20.5b, up $8b on the original price tag.

Sydney Metro West has overrun initial estimates by $12b to $25.32b, a government statement said on Thursday.

After taking over the program from the previous coalition government, Labor Premier Chris Minns said it has been plagued by cost overruns and significant time delays.

"This review is about assembling the right rescue team to come up with solutions to literally get the Metro project back on track," he said.

"We're not interested in casting blame - we're interested in finding solutions."

The independent review will examine how the projects are delivered and analyse which government departments are involved, as it looks to "resuscitate" the state's transport infrastructure pipeline.

It will be led by eminent transport public servant and former federal infrastructure department head Mike Mrdak and former senior official in Queensland's transport department, Amanda Yeates.

NSW Transport Minister Jo Haylen said her department had inherited significant challenges with the Metro project and across transport more broadly.

"Given the significant investment in the Sydney Metro to date ... an urgent independent review into the whole Sydney metro project is appropriate and warranted," she told reporters on Thursday.

The revised, estimated cost for the Metro City and Southwest links of the metro projects have also ballooned by $2b since the Perrottet government's June 2022 budget priced the project at $18.5b.

The former government had calculated its total on the assumption it could recoup $1.6b by selling businesses and properties compulsorily acquired along the line.

During the election campaign, then-premier Dominic Perrottet defended the cost of the Metro projects by saying they would reshape the city for the better.

"We have to future-proof western Sydney," he said.

In addition to cost blowouts on the Metro line, lengthy shutdowns required on parts of the Sydney train line were not made public by the former government.

Briefings given to the Minns government claim Metro works will require a 15-month closure of the T3 line between Bankstown and Sydenham.

The review team will deliver an interim report to the government before the budget is handed down, and deliver its final report by the end of 2023, Ms Haylen said.

Business Western Sydney said it did not support the shelving of any of the Metro lines but supports more transparency around the transformative projects that will change how Sydneysiders move around.

"We should be given the details of these projects so we can be sure that we get station locations, housing supply and job creation right," executive director David Borger said.