The rail safety regulator is investigating allegations of fraud by labour hire companies involved in Victoria's 'big build' projects.
Project managers on the Metro Tunnel and level-crossings removal program have been billed for up to three shifts reportedly performed by one worker in a 24-hour period, the Herald Sun reported on Friday.
The Office of the National Rail Safety Regulator (ONRSR) confirmed it was investigating the allegations.
"ONRSR is aware of allegations relating to fraudulent practices by labour hire companies contracted to major projects and railway operations in Melbourne," a spokesman told AAP.
"These allegations are currently the subject of an ONRSR investigation, with the focus of our activities being on safety matters."
The regulator could not comment on specifics while the investigation was ongoing, but the spokesman noted labour hire companies had safety duties under Australia's Rail Safety National Law.
"Should any breach of (the law) be identified, ONRSR has at its disposal a full range of enforcement powers," the spokesman said.
"These include the ability to undertake legal proceedings and the provision to prohibit unsafe operations."
The regulator is probing claims of underpaid allowances to workers among the allegations, along with claims of "ghost shifts" where shifts are not filled despite workers being rostered on.
Despite the government unveiling a $31.5b COVID-19 debt repayment plan in Tuesday's budget, global ratings agency S&P warned record spending on Victoria's big build will ensure the state's cash deficit remains large.
Premier Daniel Andrews has denied his government should have scaled back infrastructure spending to make a bigger dent in net debt, which is forecast to top $171.4b by mid-2027.