Authorities have banned two foreign-flagged ships from Australian ports after their crews reported being underpaid hundreds of thousands of dollars.

The Chinese-owned bulk carrier MV Xing Jing Hai and the Panama-flagged MV Fortune Genius were banned for 18 months and 12 months respectively.

Australian Maritime Safety Authority investigators found the crews were owed about $240,000 in unpaid wages.

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"Failure to pay crew their wages in full and on time is a reprehensible breach of the Maritime Labour Convention," AMSA operations manager Allan Schwartz said in a statement on Friday.

"The operator of the Fortune Genius has acted in a dishonest and predatory fashion towards its seafarers."

Investigators found the crew had been underpaid by about $100,000 and the ship had been using two sets of wages books - one showing what crew should have been paid and another showing what they'd actually been paid.

Mr Schwartz said the Xing Jing Hai had also demonstrated a systemic failure to ensure its seafarers were paid properly.

"These two operators will not make a profit in our waters on the back of modern-day slave labour," he said.