Melbourne’s Metro Tunnel will open in December this year, Victorian Premier Jacinta Allan has revealed.

The project has been plagued by delays and cost blowouts since it was announced in 2015.

The government announced earlier this week that all five Metro Tunnel stations were now complete, after construction finished on the Town Hall and State Library stations in the CBD.

In a post on social media platform X, Ms Allan said the tunnel would open later this year.

“EXCLUSIVE: Metro Tunnel is opening in early December,” Ms Allan said.

The premier told ABC Radio Melbourne on Tuesday morning: “It’s tremendously exciting to be getting so close to the opening of the Metro Tunnel.”

Ms Allan would not give a precise date for the opening of the tunnel, only repeating it would be in “early December”.

“There’s some further finalisation of the appropriate accreditation processes,” she said.

More details are expected to be revealed later today.

In June, the government was forced to deny reports the tunnel would not be fully operational when it opened.

It was reported that some train services would run through the nine-kilometre twin tunnels this year but peak-hour services would divert to the City Loop until early 2026, despite the project being spruiked as opening this year.

It was suggested the delay was due to construction of two of the project’s five underground stations — Town Hall and State Library — failing to meet completion deadlines.

A sign saying state library.

The State Library station was among the final two new stations to be completed. (Supplied: Victoria government)

This week, the government said the stations were now complete.

“It’s no coincidence that the 2 city stations were the last to be completed. The CBD location, along with their depth always meant a longer and more complex build compared to Arden, Parkville and Anzac stations,” the government wrote on its Big Build website.

Metro Rail has notched up hundreds of millions of dollars in cost blowouts and there were already known issues with station construction, including a shortage of construction workers, supply chain constraints and disruptions caused by COVID-19, that had pushed back the opening date.