The CFMEU is considering launching a High Court challenge over the dismissal of two former officials who broke union rules.
The Federal Court on Wednesday rejected the CFMEU's appeal to a ruling that found Andrew Quirk and Brian Miller should not have been dismissed from the union.
The CFMEU argued the two men broke union rules by appearing in the media without permission and making false allegations.
CFMEU National Secretary Zach Smith said the union was looking at its legal options closely.
"The CFMEU is seriously considering appealing this decision in the High Court.
"We completely reject Acting Chief Justice Rares' insinuation that any inappropriate conduct occurred.
"We maintain the extremely strong view that these men are not and never were whistleblowers.
"Appearing in the media with no permission from the union and making false allegations does not make you a whistleblower.
"Our union has rules in place about gross misbehaviour for a reason.
"Making false allegations can tarnish or ruin reputations of our hardworking members and officials.
"If our High Court appeal goes ahead, we'll be seeking a stay of the payment of damages."
