Prime Minister Scott Morrison will formally lock in his government’s support on Wednesday for Melbourne’s long-awaited $13 billion airport rail link .

The signing of a formal heads of agreement between the Victorian and federal governments commits the two parties to a start date for work on the long-awaited infrastructure project.

The signing ceremony between Mr Morrison and Premier Daniel Andrews in Melbourne on Wednesday will also put the Prime Minister’s own political signature on the high profile transport project, boosting his infrastructure credentials for the upcoming federal election battle.

The agreement commits the two parties to have a full business case ready within about 12 months and be able to break ground on the rail line, which has been on and off the agenda for decades, within three years.