WA protesters crash Roe 8 announcement

Protesters have drowned out West Australian Premier Colin Barnett at a press conference to announce contract details for the contentious Roe Highway extension project.

More than 20 protesters hijacked the event where Mr Barnett and Transport Minister Dean Nalder named Leighton Contractors to lead a consortium of contractors on Roe 8.

Greens MP Lynn MacLaren, who was among the protesters, told AAP that Mr Barnett and Mr Nalder were visibly annoyed by the commotion.

Mr Barnett said the contract would be signed later this year, with construction to begin in early 2016.

"Roe 8 will take 5000 trucks off local roads and make it easier for people to access Fiona Stanley Hospital while delivering faster journey times for people who live and work south of the river," he said.

Opposition leader Mark McGowan called on the government to reconsider the project, saying Mr Barnett should focus on constructing a new, large port south of Perth, rather than building a road to Fremantle Port, which was already close to capacity.

"If they build this road it will just mean they delay the construction of Kwinana Port, they delay the real solution to the freight issues confronting Perth," Mr McGowan said.