All of the vessels were foreign-flagged and most were coal ships, and were detained in the port for a few hours to about 11 days.

A number were delayed from leaving the harbour because of the detentions.

In two of the more serious cases of last year, the Megah Tiga, a flag of convenience vessel, and the Achilles, both carrying ammonium nitrate, were declared unseaworthy after the Maritime Union tipped off the Australian Maritime Safety Authority.

Another ship loaded with ammonium nitrate in Newcastle, the Pacific Adventurer, was declared unseaworthy when it arrived in Brisbane in March last year after enduring gales and spilling 31 containers of the substance and 270 tonnes of oil off the Queensland coast.

Since October 2006 to November last year, 53 vessels have been detained in Newcastle following inspections, according to safety authority figures.

Data for last month was unavailable.

The detentions were for defects that included faults with lifeboats' release mechanisms, engine-room fire dampers, which prevent air entering a particular space, wasted cargo hatch covers and poor maintenance.

In three cases last year, a ship was held because its oily water separator discharge contained more than 15 parts per million of oily substance, or the device was faulty.

Ships can pump water from their bilges provided it is done through the filter, to prevent pollution.

While the number of detained vessels was low compared to the thousands that visit the port, the International Transport Workers Federation described the defects as concerning and said more surveyors were needed as only a small portion of vessels moving through the country's ports were inspected.

The authority has three full-time surveyors in Newcastle. Last year it inspected 347 vessels in Newcastle, up from 286 in 2008. Vessels are targeted on risk categories.

The Federation also wants the Commonwealth to prevent "flag of convenience" vessels, which fly the flag of a country other than the country of ownership, from carrying high-risk cargoes in Australian waters, arguing the vessels are often sub-standard.

Federation executive officer Dean Summers said Australia's shipping industry had to be rebuilt after being decimated by Howard government legislative changes, with fewer than 50 Australian-registered ships in service.