Melbourne tunnel 'worse than Berlin Wall'

The proposed plan for Melbourne's $9 billion rail project would divide the city like the Berlin Wall during its construction, Premier Denis Napthine says.

Melbourne's Metro Rail project involves a nine-kilometre tunnel cut through the inner city, creating a handful of new stations while connecting two main rail lines.

But preliminary design work on the $9 billion project has found its construction will require a major CBD road, Swanston Street, to be shut down for at least two years.

The city's busiest intersection, outside Flinders Street Station, will also need to be dug out as crews build the massive tunnel.

The premier is asking for other options.

"Having a massive hole dividing Melbourne would be worse than the Berlin Wall," he told reporters on Monday.

"It would be absolutely detrimental to the operation of Melbourne, to the economy of Melbourne."

But when pressed, Dr Napthine could not rule out having to stick with the current plans.

He did not commit to releasing final design plans before the state election in November either.

"We're working on it," he said.

The state opposition backs the Metro Rail project but the federal government has repeatedly ruled out funding urban rail.