Metro Trains is investigating claims of bullying and harassment amid allegations staff are being pressured to strike during the Melbourne Cup carnival.
Melbourne's train operator is investigating after some train drivers claimed they were being urged to refuse overtime or call in sick during the city's Cup Carnival.
Metro Trains says claims of bullying and harassment are in relation to unprotected industrial action.
"We have received a small number of reports from our staff and are investigating them," Metro spokesman Marcus Williams said.
"We are working closely with our drivers and staff to get passengers where they need to go."
Metro had to cancel or delay numerous trips this week, mainly due to a lack of drivers.
The Australian Rail, Tram and Bus Industry Union denies its members are involved and blames driver absences on rostering issues.
"People are genuinely fatigued," locomotive division secretary Marc Marotta he told 3AW
Metro is now reassuring race goers there will be enough drivers and train services to Flemington for the Melbourne Cup Carnival.
The event attracts more than 320,000 people.
Liberal transport spokesman David Hodgett said the state government must act before the carnival is "plunged into chaos by striking train drivers".