The Singapore-registered ship and its Filipino crew are preparing to replace Alcoa's MV Portland and its 40 Australian crew members, sparking an industrial and political battle that will be aired at a senate inquiry next week into "Flags of Convenience" ships.

As the campaign against cheap foreign crews on Australia's coastal routes grew, the federation said its inspectors had been unable to find any evidence the Burmese crew of another foreign ship that carried petroleum coke to Alcoa's smelter last week had been paid since September.

Unions claim that opening Australia's coastal route to foreign crews - who do not require the stringent security checks that Australian seafarers must undergo - is a potentially serious threat to Australia's national security.

The crew of the MV Portland, defying orders from the Fair Work Commission and upheld by the Federal Court, are refusing to sail their ship to Singapore, where it is to be sold, leaving them jobless.

The 27-year-old MV Portland has been moored for more than two weeks in Portland's harbour. Alcoa argues it will save $6 million a year by scrapping its ship and chartering a foreign vessel.

The Federal Opposition's transport spokesman, Anthony Albanese, sent a message of support on Friday to the protesting seamen, calling on the Turnbull Government to withdraw the "temporary" licence allowing Alcoa to use a foreign ship and crew on the coastal route.

Independent Senator John Madigan attended a harbourside rally in Portland and said he had empathy for all concerned, including Alcoa, which was facing tough market pressures. There was no simplistic cure for what was a complex problem, Senator Madigan said. However, he was concerned at Australia's long-term prospects if ports and shipping were handed over to the control of foreign interests.

The Senate on Thursday rejected the government's proposed Shipping Legislation Amendment Bill, which Mr Albanese described as "an ideologically-driven attempt to destroy the Australian domestic shipping industry".

The Bill would have allowed foreign flagged ships paying third-world wages to undercut Australian-flagged ships on the domestic cargo trade, he said.

Deputy prime minister Warren Truss argues new legislation is needed to replace arrangements enacted by Labor, which he says has led to the Australian merchant fleet halving from 30 to 15 ships in less than  a decade.

The Australian national co-ordinator of the ITF, Dean Summers, said federation inspectors in Kwinana, Western Australia, had identified a ship named Strategic Alliance as the Flag of Convenience replacement for the MV Portland.

Strategic Alliance had a US owner, was registered in Singapore and the entire crew was from the Philippines.

The seamen earned $US618 a month basic salary and their contracts required them to stay on board for 10-11 months before they would receive any leave, Mr Summers said.

He said another bulk carrier named the K&A SE, which had carried coke from Newcastle to Portland, had been inspected in Portland on November 20.

It was owned by a Japanese company, sailed under a flag of convenience from Panama and its entire crew was Burmese.

The ITF inspectors had found "no wages had been paid since the end of September, no overtime had been paid. which constitutes a big part of the crew members' wages and there was no evidence of  earlier wages being sent home to their families (allotments)."

The Age emailed questions about the allegations to the company said to have recruited the crew, SellysArt Marine, of Yangon, Myanmar. No response had been received at time of publication.