Brisbane 2032 projects may be delayed amid legal chaos after a new-look building and construction code was proposed, unions say.

Submissions for an amended code that would apply to Queensland government projects that exceed $2 million have been sought amid the state's CFMEU inquiry.

The previous Best Practice Industry Conditions (BPICs) under Labor were scrapped by the Liberal National government, which said they had been a factor in major project cost blowouts, calling it the "CFMEU tax".

The CFMEU inquiry is accepting submissions on a potential new guidelines until July 24.

However, Queensland's Council of Unions is concerned a new code may shut out big builders and disrupt multi-billion-dollar infrastructure like 2032 Olympic projects.

QCU general secretary Jacqueline King feared the proposal "conflicts with federal laws", prompting her to reach out to the Workplace Relations Minister Amanda Rishworth.

She has also asked Queensland Deputy Premier Jarrod Bleijie to explain the changes, saying the industry had been thrown into confusion.

"There's definitely a high risk that some of those projects will be pushed back if the government continues down the track that it has," Ms King said on Wednesday.

"It's a real dilemma for employers ... to know what can they legally do, and what can they do to actually win those tenders, and then operate on that basis."

The proposed code may ban a range of lawful conditions in federally approved enterprise agreements, she said.

Ms King said a draft code released through the inquiry cut across the federal Fair Work Act, particularly on delegate rights, skills and training and project-wide agreements, and could invite constitutional and administrative law challenges.

"There's a lawyer's picnic here in terms of what they've proposed with the draft code," she said. 

The union is prepared to mount legal challenges and broader campaigns to defend conditions it argues underpin safety, training pipelines and productivity on large projects, including Olympic venues.

The LNP government on Wednesday denied reports it was banning contractors with CFMEU agreements, saying it would rely on site-specific enterprise agreements that do not include them.

"We can confirm we're not banning contractors. There'll simply be site-specific (agreements) for 2032 and beyond venues, that obviously won't include BPICs," a government spokesperson said.

Mr Bleijie said best-practice conditions had been created for Labor's CFMEU mates, causing cost blowouts and years of delays on government projects.

"The Crisafulli government is committed to restoring safety and productivity on Queensland job sites," he said.