Colin Barnett has declared the Roe Highway stage 8 extension will not be built in this term of Government, sparking accusations by the Opposition of yet another broken commitment.
Roe 8 is politically explosive in many southern suburbs.
Proponents insist it will separate heavy truck traffic from suburban roads and opponents describe it as a "road to nowhere" that will destroy sensitive wetlands at Beeliar.
The Liberal Party has campaigned on building Roe 8, a 5km extension of the highway from the Kwinana Freeway to Stock Road, at consecutive elections.
But there is no money in the State Budget for the project, expected to cost more than $600 million, and now the Premier says it will not be built before 2017.
"Roe 8 won't be built in my view in this term of Government but it remains an important road project for the efficient operation of the metropolitan area," Mr Barnett said yesterday.
"We've just got a lot on our plate and that's a very big road project.
"We and the Commonwealth have committed to the Swan Valley bypass project, we've committed to extending the freeways, we've committed to major urban rail projects and amongst all that, at some stage, Roe 8 comes into play.
"But it's not going to be one of those earlier projects."
Labor is opposed to construction of Roe 8 but panned the Government for breaking its commitment.
In question time, Opposition Leader Mark McGowan produced an election advertisement from Riverton MLA Mike Nahan that declared: "The Liberals will build the Roe 8 extension to alleviate traffic congestion."
Shadow transport minister Ken Travers said the Government did not understand it was obliged to honour its election commitments.
"It is clear now that the Roe 8 promise has followed the same fate of the Liberals' promise to build the Ellenbrook rail line in 2008," Mr Travers said.
Greens MLC Lynn MacLaren said opponents of the project would be relieved."Hopefully the Premier will use this extended time to consider dropping the project," she said.