Opposition leader Colin Barnett has backed the immediate construction of a new 300MW coal-fired power station in Collie to be followed by the construction of a 240MW gas-fired plant in Kwinana. Both plants would be owned and run by government-owned utility Western Power.

But this would scrap Western Power's existing power procurement process. Three groups – two coal and one gas – have been shortlisted to build the new 330MW baseload station. The preferred tenderer is to be announced next September.

Ripper said this could lead to legal action against the State and delays in proceeding with the project.

"The last time Mr Barnett interfered in a tender was when, as Energy Minister in the Court government, he broke a pre-election promise and halved the size of the planned 600 megawatt coal-fired Collie power station to 300 megawatts," he said.

"The project ultimately cost twice as much as it should have and we are still paying off the debt."