Phone taps have caught a construction union boss calling a colleague “a dog” and threatening to bash him.

Construction union boss Brian Parker wanted to “bash” a colleague who had previously raised questions about the union’s ties to underworld figure George Alex, taped phone calls have revealed at a corruption inquiry.

In an extraordinary day at the unions royal commission, a phone call recording obtained by the inquiry revealed Mr Parker calling fellow Construction, Forestry, Mining and Energy Union official Mario Barrios a “f***ing dog”.

Mr Barrios is a CFMEU organiser who gave evidence he had received a threatening phone call from Mr Alex in August.

Mr Alex, who is himself due before the commission in October, asked Mr Barrios why he was “talking so much s*** about me” and told Mr Barrios “I want to come and see you”, Mr Barrios said.

Mr Barrios reported the call to the police.

Days before the call, Mr Barrios had complained to Mr Parker, the CFMEU NSW secretary, about the union supporting a workplace agreement with Capital Labour Hire, a company he suspected had links to Mr Alex who was known for “phoenixing” companies and not paying worker entitlements.

Mr Parker told the inquiry he and Mr Barrios had a very close relationship, minutes before the recorded phone calls were played.

In one, recorded on August 28, he told another CFMEU official he had to restrain himself from bashing Mr Barrios.

“The problem is if I end up doing it … he’ll end up doing a stint in hospital,” Mr Parker said.

In a call to his daughter recorded on September 7, Mr Parker made the reference about Mr Barrios being “a f***ing dog”.

Counsel assisting the commission Jeremy Stoljar SC asked Mr Parker if he was angry because Mr Barrios had gone to the police and co-operated with the commission.

“No, no, no, I say things in the heat of rage,” Mr Parker said.

The commission has heard allegations that the CFMEU received kickbacks of $2500 a week from companies linked to Mr Alex.

Under questioning, Mr Parker said he had never received payments and had no knowledge of other officials taking money.

The hearing was interrupted by the surprise arrival of businessman, convicted criminal and former bankrupt Jim Byrnes at the commission, who gave unscheduled evidence that he had seen another CFMEU official receive money at Mr Alex’s house.