A proposal to build a rail line to Melbourne Airport through a public-private partnership will receive $10 million in next week's state budget.

The Andrews government made a surprise announcement on Sunday that it will conduct a "detailed assessment" of the best route for the rail link, its estimated cost and how best to pay for it.

Credit:Chris Hopkins

The plan to investigate the rail link comes after Prime Minister Malcolm Turnbull said recentlythat the lack of an airport rail in Melbourne was an "omission".

It has been reported that the federal budget on May 9 could contain as much as $1 billion for rail to Melbourne Airport, even though it is not a confirmed state government project.