The court ruled that assistant immigration minister Michaelia Cash had over-extended her ministerial powers last year by granting work rights to offshore employees, one day after the Senate rejected similar legislation.

The Australian Petroleum Production and Exploration Association said the Federal Court decision has the potential to shut down operations and undermines Australia’s international investment reputation.

“The oil and gas industry is currently developing around $180 billion worth of projects in Australia and has generated 100,000 additional jobs across the economy,” the group said in a statement.

“Many of these projects – and the Australians they employ – depend on the specialised work performed by international workers who are critical to the safe and efficient operations of vessels that perform vital services such as pipe-laying, dredging and the installation of subsea equipment.

“The Maritime Union of Australia’s campaign against these specialised temporary workers is damaging the national interest and the long-term interests of its own members by putting projects at risk.

“These highly specialised overseas workers are not taking the jobs of Australia workers, they are meeting the temporary needs of the massive resource projects that are helping to grow our economy.”

The Australian Mines and Metals Association said the practical effect of the decision jeopardised thousands of jobs in the offshore resource sector.

“Due to the maritime unions’ crusade against any non-Australians working in our offshore resources sector, the industry is again thrown into uncertainty and the government is again forced to find a quick fix to a legislative mess unnecessarily created by Labor and the unions,” AMMA executive director Scott Barklamb said.

The MUA argues that employers did not look closely at Australian workers who could undertake the same work before looking overseas.

MUA national secretary Paddy Crumlin said the unions did not have a problem with a temporary migration program that genuinely filled a gap in skills if it properly engaged in market testing, but he said the issue wasn’t about a skills shortage, but about employers looking to import overseas workers on cheaper wages.

Senator Cash said she was considering how to respond to the judgment but stressed hoped to “restore certainty” to the offshore oil and gas industry.

ICN sister publication Energy News understands the Commonwealth may have prepared a temporary legal instrument to give the employees protection and allow them to remain insured, while it considers an appeal to the High Court.