Opposition frontbencher Brendon O'Connor concedes the record fines of $2.4 million imposed on the CFMEU last week would not have been as stiff under a Labor government.
But Labor's employment spokesman says he won't be lectured by a federal government on the rule of law when its Employment Minister Michaelia Cash has presided over a "vigilante agency" and has questions to answer of her own over the resignation of the head of the building and construction watchdog.
"People have to suffer the consequences of breaking the law," he told Sky News on Sunday.
However, he added: "The penalty may have been different (under Labor)."
Meanwhile, Labor continues to pressure Senator Cash for a better explanation surrounding the resignation of Nigel Hadgkiss, who stepped down as the Australian and Building Construction Commission chief last week after he admitted to breaching the Fair Work Act.
Mr O'Connor said it is "quite remarkable" she wasn't aware of the extent of the wrongdoings of Mr Hadgkiss.
"The ABCC was created in December last year and Mr Hadgkiss was appointed as regulator of the ABCC even though legal proceedings of a serious nature were a foot about his conduct," he said.
Senator Cash told parliament last week she had known about the matter since October 2016, but denied it meant she knew of the breach until Mr Hadgkiss resigned.
In court documents, Mr Hadgkiss admitted that in December 2013 he directed Labor government changes to right-of-entry laws - which were due to come into effect in January 2014 - not be published by the Fair Work agency which he headed at the time.
The coalition won the federal election in September 2013, promising to repeal the laws.
ACTU president Ged Kearney said such actions strengthened the case for a national corruption commission.
"I would hate to see what she (Senator Cash) would say if the union movement made a similar action as to that," she told ABC television.
But Australian Chamber of Commerce and Industry chief executive James Pearson said Mr Hadgkiss, a distinguished and long-serving public servant, has resigned faced with these allegations.
He said there were many officials of the CFMEU who did not resign in the face of allegations and instead went out and ignored the law.
"Who have to be taken to court at considerable public expense, who are regularly found guilty, who are subject to fines totalling now in the tens of millions of dollars," Mr Pearson told ABC television.