Tuesday's budget will for the first time lock in federal funding for Melbourne's controversial East West Link, ignoring the Andrews government's decision to scrap the project and blighting hopes on Spring Street of negotiating other uses for the federal funds such as Melbourne's $9-$11 billion Metro rail project.

The East West Link money, $3 billion in total, will be listed in the federal budget's "contingency reserve" and held in a form of escrow, meaning it can be drawn down only for that project and would be accessible to whichever party commits to building it.

Tony Abbbott announcing federal Coalition backing for the East-West tunnel. Credit:Justin McManus

However it remains possible that half of the funds could be approved for Transurban's recent proposal to build a toll road similar to stage II of the East West Link.

Prime Minister Tony Abbott acknowledged on Melbourne radio that Transurban's proposal was not "dissimilar" from the western part of the East West Link to which he has committed $1.5billion.