Building inspectors were abused, photographed and had personal details read out by union officials in aggressive clashes at construction sites, an inquiry into trade unions has heard.

Video evidence tendered to the Royal Commission into Trade Union Governance and Corruption captured Fair Work Building Inspector Seamus Flynn repeatedly being called a “f***ing piece of s***” by officials from the Construction, Forestry, Mining and Energy Union (CFMEU).

Mr Flynn told the commission he confronted three CFMEU officials at the Ibis Hotel construction site in Adelaide in May, 2014, after site managers advised the union had entered without permits.

He located the officials in a hallway of the building and took photographs of them, sparking abuse from one, John Perkovic.

Video recorded by Mr Flynn’s colleague, Angeliek Peters, and played at the hearing, captured the confrontation.

In his statement, Mr Flynn said Mr Perkovic “quickly moved towards me, saying `you f****ing maggot, what are you taking a photo of me for you piece of s***'”.

Mr Flynn said Mr Perkovic, who was taller and larger than him, came close and pushed against his stomach with his body, pushing him backwards.

On the video, Mr Perkovic can be heard saying: “You f***ing coward, I’d f***ing take you to school, you f***ing piece of s***”.

In another incident, Fair Work Building Inspector Matthew Barr told the inquiry he and his colleagues were repeatedly called “dogs”, spat at and intimidated on visits to the Barangaroo construction site in Sydney in July, 2014.

Mr Barr said he went to Barangaroo to investigate unlawful industrial action.

Mr Barr said when workers attended a 6.30am meeting outside the building site, CFMEU official Luke Collier singled out fellow inspector Jared O’Connor, using a megaphone to address the crowd.

“That grub Jared O’Connor is here,” Mr Collier allegedly said, and read out Mr O’Connor’s mobile phone number to the crowd.

“Why don’t you give him a call and let him know what you think.”

At another meeting a few days later Collier said: “Jared you think all I got is your phone number?”

Mr Barr said he and his colleagues were repeatedly referred to as “dogs” in statements such as “don’t stand too close, Mick, they have fleas, they’re dogs”.

Counsel assisting the commission Jeremy Stoljar SC said the inspectors faced situations where they were outnumbered by CFMEU officials and members and encountered behaviour the broader community would find “offensive and thuggish”.

“However it is worse than that. It may be conduct which the law regards as criminal,” he said.

The hearing continues.