Coalition MPs in marginal seats are facing a campaign by the cashed-up Maritime Union which claims the Turnbull government is overseeing a jobs market in which people can be "sacked for being Australian". 
An advertising blitz beginning Monday will pinpoint some of the Coalition's most vulnerable seats in areas affected by the declining coastal shipping industry.
They include the Victorian electorate of Corangamite, held by Liberal Sarah Henderson, Tasmanian seats Braddon and Bass and Capricornia, the north Queensland electorate of the LNP's Michelle Landry.    
The MUA's TV and radio campaign focuses on the experience of the crew of the  MV Portland.
In   January, after 27 years of hauling alumina between Western Australia and Victoria for mining giant Alcoa, the MV Portland's Australian crew were marched off the ship by 30 security guards, ending a two-month on-board protest.
The MV Portland was sailed to Singapore to be scrapped and Alcoa received approval from the federal government to replace it with a foreign-crewed vessel on the same route.
The mainly-Filipino crew members of the replacement ship are paid about $150 a week, according to the International Transport Workers Federation.
Despite the Senate blocking former deputy prime minister Warren Truss' bid to open the Australian coast to more foreign-flagged vessels, the government has continued to issue one-off, "temporary coastal licences" for foreign-crewed ships. 
This month, armed police removed another Australian crew from the bulk alumina carrier CSL Melbourne which had  been chartered by Pacific Aluminium, a wholly-owned subsidiary of Rio Tinto.
It has been replaced by a low-paid foreign crew on its former route between Gladstone in Queensland and Newcastle.
The campaign will be launched at the MUA's national conference on Monday.
MUA national secretary Paddy Crumlin said the ads would hit home with ordinary workers because if it can happen to seafarers it can happen to anyone.
"Everyday Australians don't accept a government that is actively destroying the jobs of its own people," he said.
"The ships don't leave Australian waters, and should be crewed by Aussie seafarers. These blokes have been sacked for being Australian.
 "This is a message that we will be taking to every community before the federal election and making sure that people know that the Turnbull government is selling off Australian jobs."
In the United States, coastal shipping laws dictate that every crew must be American, every ship must be American-owned and must have been built in an American shipyard.