During cross examination on Tuesday, Tom Roberts, a senior legal official with the CFMEU, conceded he had accepted the word of senior officials at face value without checking important facts.

Mr Roberts assisted with the internal investigation into allegations that former union officer Brian Fitzpatrick received a death threat from Darren Greenfield, his colleague at the time.

Mr Fitzpatrick has told the royal commission he received the death threat on March 27 last year after he tried to stop his union dealing with Sydney crime figure George Alex.

Mr Fitzpatrick claimed union officials wanted to "get rid" of him "because I wouldn't drop off the George Alex business".

He alleged that Mr Greenfield called him and screamed with "absolute rage" words to the effect of: "You have gone too far this time you fat c---. You're dead. I'm coming over there tomorrow and I'm going to kill you."

Senior counsel Jeremy Stoljar questioned Mr Roberts about an internal investigation into the allegations and suggested it was "simply a whitewash". This was rejected by Mr Roberts.

"My proposition to you, Mr Roberts, for your comment, is that this report just skates over and doesn't delve into the real issues confronting the branch," Mr Stoljar said. "Do you agree with that?

"No I don't," Mr Roberts replied.

Mr Stoljar asked a series of questions about whether crucial facts under investigation had been checked, to which Mr Roberts replied in the negative.

Mr Stoljar said Mr Roberts simply accepted what he was told by senior officials including the union's NSW secretary Brian Parker and NSW president Rita Mallia.

"You just accepted what Ms Mallia told you, you didn't investigate it at all. It wasn't a serious investigation, was it, Mr Roberts?" Mr Stoljar said.

"Of course it was a serious investigation," Mr Roberts said.

In a letter to national CFMEU secretary Michael O'Connor in October last year, CFMEU officer Andrew Quirk said Andrew Ferguson, then a CFMEU official, "overrode" Mr Fitzpatrick's objections to the union signing an enterprise agreement with Mr Alex. The negotiations were done over lunch at Tuscany restaurant in Leichhardt.

Mr Quirk also described Mr Greenfield as "the new branch enforcer".

"The CFMEU in NSW is now at risk of becoming a front for criminal figures for the first time since the early '60s," Mr Quirk said.

Meanwhile, Employment Minister Erik Abetz was critical of the CFMEU for contacting him on Tuesday to raise concerns about sham contracting arrangements involving workers on 457 visas.

CFMEU national secretary Dave Noonan wrote to Mr Abetz requesting an investigation into allegations raised at the royal commission in relation to the abuse of the 457 visa system, breaches of workplace laws and tax evasion in the construction industry.

"This is the first time that Mr Noonan has written to the Minister expressing concern about allegations arising from the Royal Commission," Mr Abetz said. "The government believes that all allegations of wrongdoing in workplaces should be dealt with by the appropriate authorities.

"It is disappointing that the CFMEU appears to take a very selective approach to enforcement of workplace laws and the investigation of serious wrongdoing."

Mr Noonan said: "Erik Abetz only needs to answer one question. Will he investigate these serious allegations or not."