An artist's impression of the airport rail link station. Credit:Melbourne Airport

Melbourne Airport has called on the state government to reject a multi-billion airport rail plan that uses existing tracks, arguing that a dedicated tunnel from the city to Sunshine was a “once-in-a-generation” opportunity that ensured western suburbs commuters were not short-changed.

The state and federal governments have each pledged $5 billion to building the airport rail project but are yet to agree on the exact form the project will take.

The Andrews government insists it is considering all options but The Sunday Age reported it appeared to be leaning towards a cheaper alternative that would put trains onto congested tracks between the city and Sunshine and enter the CBD through the new $11 billion Metro Tunnel.

A government spokeswoman said all options would allow for increased train services on every train line in Melbourne's west.