The behaviour of CFMEU protesters inside a state government building was disgraceful and affected workers are owed an apology, Queensland Premier Annastacia Palaszczuk says.
Workers' safety was likely put at risk when Construction, Forestry, Maritime, Mining and Energy Union members entered the Transport and Main Roads building in Brisbane on Tuesday morning, Ms Palaszczuk said.
"No worker should go to work fearing for their safety ... it is disgraceful behaviour," she told reporters on Thursday.
"That footage is incredibly disturbing and I would have hated being a person there with that happening ... they owe an apology to those workers who were subjected to that and who felt unsafe."
Ms Palaszczuk said she understood police were looking into the matter.
Officers were called to the office building on Mary Street about 9am following reports of a large group entering the premises, Queensland police said.
"The group was monitored by officers for several hours but following negotiation a peaceful departure from the group occurred just before 12pm. No further complaints have been made," a spokesperson said in a statement.
A Queensland Transport and Roads Investment Program briefing was cancelled following the action.
More than 200 CFMEU members rallied in the department's conference room, preventing the event proceeding, a Transport and Main Roads spokesperson said.
"During this period, TMR staff were subjected to very upsetting and unacceptable behaviour," they said in a statement.
"The safety of our staff is our number one priority, and accordingly the event was called off at 9.40am but protesters remained until 10.30am."
A security guard was allegedly knocked down when union members went through the front doors, but did not appear to be seriously injured and indicated they wouldn't press charges.
Three senior members of the CFMEU had been invited to attend the briefing, the department said.
The issue "seems like a bit of a storm in a teacup" according to the union, with assistant secretary Jade Ingham describing the decision to lock down the building as irrational.
"A bunch of fluoro shirts attended the meeting and unfortunately some people panicked about that," he said on Thursday afternoon.
"Workers simply just wanted to go and listen about industry projects that were coming up.
"We attended a meeting, the meeting got cancelled and we left."
Calls for an apology came as Transport Minister Mark Bailey confirmed he met the union on Monday, but had not been told about Tuesday's plans.
"There was no indication made to me in the meeting with (CFMEU state secretary Michael Ravbar) on the Monday, he gave no indication about that whatsoever.
"If he had, I would have raised it immediately with my (director-general) and we would have made preparations to make sure that our staff were protected."
Mr Bailey said a late decision not to attend the briefing was due to a cabinet budget review committee scheduled at the same time.
He called on Mr Ravbar to make a public apology.
"I have backed in our workers from day one as their minister, I take that responsibility seriously, and they were mistreated by his union members," he said.
The opposition is calling for Mr Bailey to be stood down while a full investigation takes place.
"To organise 200 CFMEU members overnight has to be planned, and as if they didn't tell the minister," LNP deputy leader Jarrod Bleijie said on Thursday.
