Funding to duplicate train tracks in the Geelong region is expected in the federal budget in a last-ditch bid to retain Victoria's most marginal seat.
Treasurer Josh Frydenberg is expected to unveil $700 million for Sarah Henderson's seat of Corangamite, held by just 0.03 per cent, when he hands down his first budget on Tuesday.
Funding to duplicate 12.6 kilometres of track from South Geelong to Waurn Ponds will come on top of billions of dollars already pledged in a bid to save the seat of Corangamite, which takes in Geelong and the Surf Coast region.
Prime Minister Scott Morrison said the $700 million will be set aside for Geelong regardless of whether the Liberals retain the seat at the upcoming federal election.
"We are committed to the satellite cities approach that I announced as part of the population management plan, whether it's the fast rail that connects up Geelong, whether it's the increased investment in the Waurn Ponds line, whether it is the north-south rail links. These are all about managing Australia's population growth," he told reporters.
Mr Morrison has already announced $2 billion for a fast-rail link between Geelong and Melbourne, with the long-term project reliant on Victoria matching the federal commitment.
But Victoria has accused Mr Morrison of jumping the gun on the project, with the state government already spending $50 million investigating how to make it work.
Victoria's Transport Minister Jacinta Allan said the state government is continuing to plan and consult with the community to deliver fast rail to Geelong.
"We do want to see the fastest travel time possible between Geelong and Melbourne, but what we won't do is try and deceive the Geelong community about what actually can be achieved," she told reporters on Monday.
"A lot of numbers have been thrown around in terms of what the travel time should be between Melbourne and Geelong, but this big and important project needs to be planned properly."