Plans to build a light rail link to Perth's northern suburbs have been abandoned, the West Australian Government has confirmed.

The decision comes as the Government prepares to release its long-awaited transport plan, and three years after it went to the 2013 election promising a "fully-cost, fully-funded" MAX Light Rail to Mirrabooka.

Transport Minister Dean Nalder said there would be a transport corridor to the north, but no light rail.

"And what you will find in this transport plan is a transport corridor to the north designed for transporting people," he said.

"I don't want to get into the level of detail around that but when I release the transport plan, it will be obvious at that point."

But pressed by reporters on whether the plan included the Government's promised MAX Light Rail project, the Minister revealed the concept had been abandoned.

"The light rail to the north I can confirm won't be done as a light rail," he said.

Minister coy on transport plan detail

Mr Nalder has yet to release the report, but details of the plan have been leaked to the ABC.

Those papers include a proposal for an East-West City Link to ease congestion on existing Swan River crossings east of the CBD, including the Graham Farmer Freeway and the Causeway.

An East-West City Link is planned to help reduce Graham Farmer Freeway traffic. ( ABC News )

The link was one of a vast number of projects in the plan that mapped out what transport infrastructure could be needed with the state's population expected to reach 3.5 million by 2050, an increase which could result in more than 12 million trips every day in and around Perth.

Meanwhile instead of MAX Light Rail, there is a proposed light rail linking across the city centre, stretching from the University of WA and QEII Medical Centre to Curtin University and Canning Bridge.

After initially promising light rail and then considering a rapid transit bus system, the plan proposes servicing north eastern suburbs with buses, and creating an underground heavy rail link to Morley.

Quizzed by reporters on specific elements of the plan, Mr Nalder declined to elaborate on the details prior to its release in mid-July.

"You're getting into details that I haven't released at this point in time and its amazing how good news travels fast when it comes to this report," he said.

The ABC understands the plan aims to increase public transport use to 11 per cent of all-day trips, including about 65 per cent of peak period trips to the CBD.

Premier defends blueprint amid criticism

Public transport advocate Peter Newman said the plan appeared to be lacking immediate measures to deal with congestion.

"It's not enough to just dream dreams. We have to have deliverables that can start to address the issues we've got now," Professor Newman said.

However Premier Colin Barnett defended the plan, arguing it was a "detailed, integrated" long-term strategic blueprint which did not require specific funding commitments.

Colin Barnett says funding decisions should be made by future governments. ( ABC News: Andrew O'Connor )

"This a plan talking about transport out to 2050. As if you're going to allocate funding now in 2016 for 2050," he said.

"From a transport planner's point of view, it is up to the Government of the day to decide which projects it will commit to in that normal term of government timeframe."

The Opposition said the leaked details proved the Government lacked credibility on public transport.

"There's so many tunnels, and roads and rail going everywhere, it's just not something you can believe they'll do. And it looks more like a 100-year plan than something the people of Western Australia can believe," Opposition Leader Mark McGowan said.

Labor's transport spokeswoman Rita Saffioti said for the plan to be believable, it needed to clearly identify project priorities, provide timelines and give accurate costings.

"In the north-east corridor [of Perth] in 2008 they promised the Ellenbrook line, they didn't deliver. In 2013 they promised a Max Light Rail, they didn't deliver. Now our understanding is they'll promise a tunnel," she said.

"So they've promised everything under the sun to the north-east corridor, they haven't delivered and congestion is getting worse."