The union crew of stranded ship - the MV Portland - were pulled off the ship by security guards, ending a blockade in a lucrative berth at the port of Portland.

The Maritime Union of Australia (MUA) and its workers have been in dispute with ship operator Alcoa, over its intention to sack the 38 crew members after a final voyage to Singapore.

The cargo ship operated for several years bringing minerals from WA to Alcoa’s Portland smelter.

The union said the crew were told to take the ship to Singapore, where they would be replaced by a foreign crew of workers paid as little as $2 an hour.

The union told its members not to embark on the final voyage, and to stay on board with the anchor down in Portland.

Reports say the security guards pulled the workers off the ship around 1 a.m on Wednesday, and it is now on its way back to Singapore with a foreign crew.

Opposition Leader Bill Shorten called it “Work Choices on water”.

“There’s an industrial dispute but that’s the tip of the iceberg,” Mr Shorten said.

“What we see is Australian seafarers, Australian jobs being replaced by foreign seafarers, foreign jobs on our coastline.

“I think there will be bad long-term consequences for Australian economy, for the Australian environment.”

But local MP Dan Tehan said unions should obey the law.

“This is a good thing for Portland and the surrounding community that the MUA can no longer hold it to ransom,” Mr Tehan said.

“The fact that the MUA had the ability to flout a court ruling for nearly two months sadly shows that there is a problem with our current workplace relations laws.”

MUA national secretary Paddy Crumlin said it was a “heavy-handed approach” to bring in security guards.

“Questions need to be asked about the role of Alcoa and the Australian Government in this,” Mr Crumlin said.

“How did the foreign crew gain permission to enter and then sail the vessel? Where are the crew from? What security checks do they have? What visa are they on?”

He also slammed a recent Federal Government decision to give Alcoa a special temporary coastal licence, allowing the foreign ship and crew to work.

“The Turnbull Government should never have issued this temporary licence to Alcoa and they should cancel it immediately,” he said.

“Australians have a right to work jobs in their own country and to be treated with respect by an employer profiting off the minerals that belong to the Australian people.”