Metalworkers have called on the Federal Government to bring forward its defence shipbuilding program, claiming the WA sector could die during a two-year lull in contracts.
The Australian Metalworkers Union claims the sector's current naval contracts are due to wind up in 2015, with the next lot of contracts not due until 2017.
AMWU Secretary Steve McCartney said 80 WA workers would lose their jobs next year under the current build schedule.
Though maintenance and service contracts would keep the other 400 or so workers going for some months, they too would eventually be made redundant.
The union put up a roadside sign near defence minister David Johnston's office yesterday as part of a long-running campaign urging him to commit local naval shipbuilding in the May Budget.
"Shipbuilders are facing a 'valley of death," Mr McCartney said.
"We need the government to make a commitment that defence projects will be built here, and to commit to a rolling build."
Mr McCartney said it was unlikely that the sector could be resurrected if the workers were lost to other industries.
Defence Minister David Johnston said future building schedule would depend on the Defence White Paper, due next year.
Mr Johnston blamed the former Labour Government for undermining the defence shipbuilding sector.
"The so-called ship-building Valley of Death was created by the former Government because rather than steering the country forward and making sound strategic decisions in defence they simply cut spending to its lowest levels since 1938," he said.
However, he recently told Australian Strategic Policy Institute's conference in Canberra that the government was reconsidering whether to deliver 12 new submarines over three decades that had been promised by the previous government.