The State Government is unveiling its billion dollar plans for a light rail network to relieve traffic congestion in Perth.

The government is proposing a 22 kilometre light rail line linking the CBD to Mirrabooka in Perth's northern suburbs and running alongside some of the city's busiest roads.

They include Fitzgerald Street and Alexander and Dianella Drives.

The line would also go to the QEII Medical Centre and east over the causeway to Victoria Park.

The Transport Minister Troy Buswell says it will cost more than $1 billion.

"It will give us the sort of public transport offerings that other leading global cities enjoy," he said.

Labor's Transport Spokesman Ken Travers says the plan is nothing more than a vote buying exercise.

"Political spin to try and convince the people of Perth that the Liberal Party has changed its spots," he said.

Mr Travers says if the Government was serious about solving the city's public transport problems, it would start by ordering enough rail cars to meet existing demand.