CFMEU protesters and workers clash at Brisbane construction site

Police are investigating an alleged brawl between union and non-affiliated members at a construction site in Brisbane on day two of strike action.

Three engineers were trying to get in to work at Cross River Rail on Cope Street about 7am today when they allegedly clashed with CFMEU protesters blocking the entrance.

Men were captured on film throwing punches in a scuffle that lasted several minutes until passersby called police.

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Police have told 9News that investigations remain ongoing. No charges have been laid.

The alleged fight drew concerns from parliamentarians.

"I think it's absolutely disgusting that the CFMEU are preventing workers going in and doing their job and earning a living for their families," deputy opposition leader Jarrod Bleijie said.

The chaotic scenes came on the second day of CMFEU protests, in which members are striking over unmet demands from CPB Contractors to deliver a 30 per cent wage increase.

The non-affiliated members are not covered by protected union action.

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CFMEU national secretary Zach Smith said union members would not be intimidated by "corporate thuggery" and refused to apologise for the alleged brawl.

"Workers have a democratic right to take industrial action when companies flat-out refuse to constructively negotiate on fair pay and safer working conditions," he said in a statement.

"This should be a lesson to employers around Australia. Our union will not be intimidated.

"We make no apology for standing firmly against corporate thuggery and using our democratic rights to achieve better outcomes for workers."

Premier Steven Miles, a proud trade unionist, faced criticism in parliament today for meeting with union boss Michael Ravbar in March but refused to apologise.

"Unions are appropriate organisations representing workers. They have a legitimate role in our society and I won't apologise for meeting with their representatives," he said.

"I'll continue to do so."

CFMEU protests will resume tomorrow until Friday.