Victorian Labor has admitted it will be difficult to deliver one of its key transport policies.

Treasurer Tim Pallas has told The Age the metro rail link will be a challenge to deliver.

“I want to be frank with people, it will challenge the government, particularly in the current economic environment,” Mr Pallas told the newspaper.

But he’s blamed it on the federal government’s refusal to help fund commuter rail and says Labor won’t give up on the project.

“Quite frankly it is disappointing for rational transport infrastructure delivery if the federal government distorts its investment into only one form of infrastructure such as roads.”

Prime Minister Tony Abbott has said $3 billion of Commonwealth funding earmarked for the East West Link would be sent back to Canberra if the road tunnel was scrapped, a Labor promise ahead of the state election.

Labor hasn’t said when the $9 billion metro rail link, which would double the size of the city loop, will be delivered.