Victoria is crucial to the May 18 election, with up to six Liberal Party seats at risk of falling to Labor. Internal polling from both major parties shows the swing against the government is larger in inner-Melbourne than other key states like Queensland and NSW. Mr Shorten's vow to contribute $10 billion towards the suburban rail loop - a massive tunnel that would link every major rail line in Melbourne as well as the new airport rail link - comes with two caveats: the money will only flow when construction commences in 2021, and it would be spent over 15 years. "I know it’s a big project, it’s a lot of money, but this is what you can do when you close loopholes for the top end of town and make multinationals pay their fair share," the Labor leader said. The cash is on top of federal Labor's pledge to spend $5 billion on the airport rail link and $2 billion to help deliver the Melbourne Metro Tunnel.

The party is now going to next Saturday's election promising at least $18.4 billion towards transport projects in and around Melbourne. Mr Morrison has promised $2 billion towards a high-speed rail line linking Melbourne and Geelong and has signed an agreement with Victoria to also provide $5 billion towards the airport rail link. Loading The proposed suburban rail loop would pass through the Labor-held seats of Isaacs, Hotham, Jagajaga, Cooper, Wills, Maribyrnong and Gellibrand, as well as through or near the boundaries of the Liberal-held electorates of Goldstein, Chisholm and Menzies. But Labor strategists believe the line is also a vote winner in other inner-city Liberal seats because it promises to ease congestion.

"If you don’t back the suburban rail loop, then you’re not backing Melbourne," said opposition transport spokesman Anthony Albanese. The Victorian government announced "the biggest public transport project in Australian history" ahead of the November state election, claiming it would be used by 400,000 passengers a day and take 200,000 cars off Melbourne’s roads. While the first stage is expected to take 10 years to build, the full project may not be finished for another three decades. The Coalition is expected to criticise Labor's promise as unrealistic given its lengthy timeline, and question whether the investment is needed given Mr Andrews has already promised to build it. "I mean you don’t come and fund projects that are already funded, you come and commit to projects that actually expand what is being done in Victoria," Mr Morrison said last week.

Mr Morrison has also earmarked $3 billion in federal funding for the East West Link, which has been scrapped by the state government but remains a priority for the state and federal Liberals. Labor's official policy costings forecast a $22 billion budget surplus in 2022 - the same year the federal funding for the suburban rail loop is slated to begin. Mr Shorten's first budget post-election would include a previously-promised $300 million for planning and design work. The Victorian-based Labor leader on Saturday accused the Coalition of cutting infrastructure investment in the state. "Scott Morrison and the Liberals in Canberra are anti-public transport and anti-Victoria," he said. Loading Replay Replay video Play video Play video