Witnesses gave evidence that the Construction, Forestry, Mining and Energy Union allegedly received a weekly kickback of $2500 from labour-hire companies linked to Sydney crime figure George Alex.

They also expressed fears for their safety.

During extraordinary evidence supporting findings unearthed by Fairfax Media investigations, the royal commission was told:

* Prison inmate Jim Kendrovski, who was assaulted in Parklea jail on Friday after being summonsed to give evidence at the commission, refused to answer questions because he feared for the safety of his wife and children.

* Union official Jose [Mario] Barrios received a threatening phone call from Mr Alex late last month after Mr Barrios raised questions with CFMEU NSW secretary Brian Parker about why the union was negotiating a workplace agreement what he suspected was one of Mr Alex's businesses.

* Convicted terrorist Khaled Sharrouf helped his mother-in-law Karen Nettleton get a job as a bookeeper for Mr Alex, an associate of Mr Sharrouf.

* Criminal identities including Sharrouf and ex-Comanchero bikie, Bill Fatrouni, were seen as guests at Mr Alex's house in Burwood where business was conducted informally.

* CFMEU NSW officials Mr Parker and Darren Greenfield were seen at meetings in Mr Alex's home.

* A director of one of Mr Alex's businesses said he started feeling uncomfortable when people from the company were being murdered - a reference to the murder of Mr Alex's standover man Joe Antoun in December last year.

The commission heard the CFMEU allegedly received a weekly kickback of $2500 from labour-hire companies linked to Mr Alex.

Under cross-examination, Michael Cohen, director of Elite Access Scaffolding, said he gave the weekly "union payment" to Mr Alex's standover man, Joe Antoun before he was murdered in December.

When counsel assisting, Jeremy Stoljar, asked whether the weekly payment was to be given to the CFMEU, he said: "To my understanding."

Pressed, he said: "That's correct", adding that was based on what Antoun had told him.

Douglas Westerway, a former director of Elite Access Scaffolding NSW, said he withdrew weekly payments of $2500, which were designated as union payments in accounting records he kept.

However, he could not confirm whether the payments were made to the CFMEU after he gave the money to Mr Cohen to be passed on toAntoun.

Mr Westerway said he saw criminal identities including convicted terrorist Khaled Sharrouf and ex-Comanchero bikie, Bill Fatrouni, at Mr Alex's house in Burwood where business was conducted in an informal way. He said he also saw union officials including CFMEU NSW secretary Brian Parker and another CFMEU official, Darren Greenfield, at meetings with Mr Alex.

Mr Westerway started feeling uncomfortable working in the business after the murder of Antoun, who had seriously assaulted him.

"People around you being murdered, it's not a comfortable place to work," he said.

While Mr Alex does not appear in company searches as a shareholder or director of the Elite holdings or Active Labour companies, Mr Westerway said he and Antoun effectively controlled the companies and how money was spent. Evidence was given that Mr Alex and Antoun received regular dividend payments of $2500.

In October last year, Mr Westerway said Antoun had discussed the need for some money for a property development in Marrickville.

But Mr Westerway indicated the company needed the funds to pay its own bills.

Antoun had seemed to have accepted this but, 10 minutes later, located Mr Westerway and assaulted him.

"Joe Antoun and somebody else came across the street and he yelled at me about being disrespectful to his wife who I hadn't even spoken to that day and told me this was my last warning and started throwing punches at me and hitting me," Mr Westerway said.

"He kept on screaming at me and telling me it was my last warning."

As a result of the assault, Mr Westerway said he went to hospital with two perforated ear drums.

Around Christmas time last year, Mr Westerway said he was buying a sandwich in Burwood when a male walked up behind him and said: "You're a smart arse aren't you?".

"He said, 'Don't f--- around with that business - it's not your business to f--- around with. This is your last warning'."

"I've had phone calls. I've had text messages."

In further evidence, Karen Nettleton said her daughter's husband, Khaled Sharrouf, was an associate of Mr Alex and had helped her get a job as an accounts clerk for Access Scaffolding, linked to Mr Alex.

Asked if she had received an explanation of $2500 described as "union payment" was – she said "no".

Fairfax Media understands Mr Alex will be called as a witness on Tuesday when hearings continue.