A ship delivering products to aluminium giant Alcoa has allegedly withheld more than $100,000 in "stolen wages" from its crew, the seafarers' union says.

The Hong Kong-registered carrier, Gold River, which hauled petroleum coke to Alcoa's Portland refinery in Victoria, is the second ship used by the company to face claims of worker exploitation in recent months.

MUA national secretary Paddy Crumlin has called Alcoa's late night raid an act of "industrial thuggery". Credit:Anthony Johnson

It has prompted union calls for Alcoa to exercise greater responsibility.

Docked in Alcoa's Portland terminal, Gold River was this week boarded by the international seafarers' union. The inspectors, who spoke with the ship's Chinese crew and audited their wage records, said the workers were owed $115,000 in wages and another $72,000 in leave and other entitlements.