The AIG says the Federal Court will open the way to a double-dipping by casuals who will now be eligible for annual leave, sick leave and other entitlements as well as the casual loading of 25 per cent that is built into enterprise agreements as part of their flexibility.

The CFMMEU has hit back, describing the AIG’s response as “hysteria” and a sign that employers are well aware of how badly “Australian workers have been ripped off by the ‘permanent casual’ trend”.

“The AIG’s own analysis shows that a majority of Australians employed as casuals work on a regular, on-going basis,” CFMMEU mineworker’s division president Tony Maher said.

“If the Skene decision has a cost impact, that shows the extent to which workers’ lost pay and entitlements have been subsidising company profits. The court has been very clear that employers can’t just label workers as casual because they want to and it’s cheaper.”

Although the union’s legal action against WorkPac, which began in 2014, has been closely watched in the Hunter and Queensland coal industries, its importance has only recently been recognised in the broader workforce. AIG said on Friday that the deadline for a High Court challenge to the decision had passed, meaning that legislation was the only way to stop the implications of the case flowing through to other industries.

“Unless Parliament acts quickly, the litigation likely to result from the decision will lead to a big increase in business insolvencies and a big blow-out in the cost of the Fair Entitlements Guarantee scheme due to claims by casuals for annual leave and redundancy entitlements,” AIG chief executive Innes Willox said.

Referring to the Adero Law case in the Hunter, Mr Willox said “litigation funders and lawyers are already planning class actions”.