A new Melbourne Metro Rail station in North Melbourne is expected to trigger $7 billion in urban development and transform the area's desolate industrial land.

But it is unclear exactly what the multibillion-dollar apartment and office suburb of Arden Macaulay will look like, or how the government plans to retain a slice of the enormous profits that are expected to flow from its transformation.

On Friday Prime Minister Malcolm Turnbull told the state government that it needed to do more work on its business case for the signature Metro project, handing over just $10 million in federal cash to help.

"What is underdone in that business plan is the way [governments] are able to capture some of the very considerable value that will be created in property values by the construction of that infrastructure," Mr Turnbull said.