Melbourne’s train network could be thrown into chaos for up to two days with the state’s public transport union gearing up to take strike action over a pay deal.

The Rail Tram and Bus Union lodged an application with the Fair Work Commission on Wednesday night to stop work for up to 48 hours after negotiations with Metro Trains broke down.

The industrial action could see frontline Metro staff stop work for between four and 48 hours, and refuse to check myki cards, make announcements and wear uniforms.

The public transport system could be thrown into chaos if the union goes ahead with planned strikes. Credit:Penny Stephens

Negotiations between the RTBU and Metro Trains have been ongoing for several months, however union delegates who work for Metro say they are on a "collision course" over the workplace agreement for frontline staff, which expires on June 30.