A bombshell court ruling will change Australian public holidays forever.

Bosses must ask workers if they wish to work public holidays before rostering them on, thanks to a landmark new court ruling.

The ruling will override whatever is written into employees’ existing contracts.

The changes come after The Federal Court of Australia found an arm of mining giant BHP had broken the Fair Work Act by forcing miners to work on Christmas Day and Boxing Day.

A total of 85 workers for BHP labour provider OS MCAP at Daunia Mine in Queensland were made to work on the two December public holidays in 2019 without any extra pay.

The court’s three judges found that it was unfair for an employer to command people to work public holidays.

The judges ruled that the Fair Work Act only allows bosses to request people work on such days.

“The intended mischief the (Fair Work Act) provision confronts is the inherent power imbalance that exists between employers and employees,” the decision said.

“By virtue of this imbalance, employees will often feel compelled, and not understand, that they have the capacity to refuse a request that is unreasonable or where their own refusal is reasonable.

“The requirement that there be a ‘request’ rather than a unilateral command prompts the capacity for discussion, negotiation and a refusal.”

An employee may “refuse the request (and take the day off) if the employee has reasonable grounds for doing so”, the judgement added.

The bombshell decision will have a knock-on effect on companies that rely on shift work.