A federal magistrate yesterday adjourned a contempt of court case against Brisbane unionist Bob Carnegie.

Construction company Abigroup has asked the Federal Magistrates Court to find Carnegie in contempt of court.

It has applied to the court to deal with Carnegie for 18 breaches of a court order preventing him from attending the Children's Hospital construction site at South Brisbane during a nine-week strike.

Defence lawyer Marcus Clayton says the order is ambiguous and incomplete.

"We will be arguing that the order which Bob Carnegie is said to have breached is unenforceable," he said.

"The court rules require warning someone that they may be punished if they don't obey the order."

Hundreds of construction workers and union supporters rallied outside the court over the last three days to support Carnegie.

The hearing is expected to resume next month.