Unions will argue nothing has changed since parliament last knocked back federal government plans to restore a building industry watchdog when they appear before a Senate committee.
Industry representatives, unions and the employment department will front a hearing into legislation to re-establish the Australian Building and Construction Commission in Canberra.
The Senate has rejected the bill once and a second knockback would deliver the Turnbull government another double-dissolution election trigger.
But it now appears the government has given up on using the bill as a trigger.
A notice of motion in the Senate shows manager of government business Mitch Fifield will move to extend sitting hours when parliament resumes on March 15 in order to consider a string of bills before the pre-budget break.
The government's proposed changes to the way Australians vote for senators will take precedence over all else, while the remainder of the bills on the list are largely non-controversial.
But draft laws to re-establish the building watchdog are noticeably absent from the list.
Parliament won't resume until May 10 - the day before the final date a double-dissolution election can be called.
"By our reading, the ABCC bill won't be a potential double-dissolution trigger because it won't be brought before the Senate for a second time before the budget," Greens leader Richard Di Natale said.
The government already has a valid trigger in the Fair Work (Registered Organisations) Amendment Bill, which aims to hike penalties for union corruption.
In its submission, the ACTU argued the threat of such an election on the basis of the draft laws demonstrated an "irrational attachment" to what, on any measure, is and was bad policy.
"No amount of paper shuffling and contortion has yielded any credible economic argument in favour of the (commission)," it said.
The construction union said the move to restore the commission was the last and most extreme vestige of the WorkChoices era.
"The bills represent the antithesis of a fair go all round in the workplace," it said in its submission.
But the Australian Industry Group cited the final report from the Heydon royal commission into union corruption, saying the case for change was irrefutable.
"In the light of the royal commission's findings and recommendations, any view that the existing laws are working effectively is simply unsustainable."