In a press conference issued on Monday, NSW CFMEU secretary Andrew Ferguson said, the CFMEU would not be intimidated or bullied after last Thursday night's car firebomb attack.

The attack to the NSW state office's headquarters, destroyed part of the building's lower level, with numerous smoke damage to the upper level.

In a strong show of defiance, and surrounded by Peter Glover of the Master Builder's Association, Mark Lennon (Unions NSW secretary), as well as religious leaders and a Maori elder from the community, many of who use the building for their various meetings, the message was clear - "We will not be intimidated."

CFMEU State Secretary Andrew Ferguson said it was a miracle no one was killed in the attack as two community groups, that included children, had left the building less than an hour before.

"Emergency services staff, unaware of the petrol drums in the car, had fought the fire and could have been killed," he said.

"We are obviously very concerned about the attack, but also the implications in terms of our democracy and the right of people to organsise around their rights," he said.

"But we will continue to do our job representing people and workers rights," Ferguson said.

The CFMEU is working very closely with the NSW police force to find the person or persons responsible.

"We will leave this investigation in the hands of the NSW police, who we are working closely with and believe are doing a good job. We are hopeful the culprit or culprits will be found soon."

At this stage, no arrests have been made.