Fast trains from Geelong would speed into the city via a new rail link connected to the proposed Melbourne Metro 2 underground railway, under a game-changing proposal being considered by the Andrews government.

Sources across industry and government say Spring Street is looking at the proposal. Melbourne Metro 2 would connect Newport, Fishermans Bend, the CBD and Clifton Hill.

Trains from Geelong would run along an upgraded section of track linking the Geelong and Werribee lines that is currently used for freight. New tracks would then be built from Werribee to Newport and link up with Melbourne Metro 2.

The proposal is understood to have been pitched to the Morrison government in a bid to win support for an above-ground airport rail link, which would mean ditching plans for a tunnel between the city and Sunshine.