Police have arrested former CFMEU organiser and former Labor Party sub-branch president Halafihi 'Fihi' Kivalu.
The former ACT Construction, Forestry, Mining and Energy Union organiser is alleged to have solicited and pocketed thousands of dollars in bribes.
Mr Kivalu was president of the ALP's Dickson-Morning sub-branch in Canberra at the time he was allegedly involved in corruption.
He appeared before the royal commission into unions hearing in Canberra on Thursday and admitted he took money from a subcontractor to help him win work. But he has denied he demanded the money or could guarantee contracts and he has contested other allegations against him..
ACT Policing issued a statement saying officers had arrested a 39-year-old Queanbeyan man after the commission hearings.
"Enquiries are continuing and it would not be appropriate to make any further comment at this point," police said.
"The Australian Federal Police Taskforce attached to the Royal Commission into Trade Union Governance is urging members of the ACT and NSW regional community to come forward and report matters relating to union governance and corruption."
During the Thursday hearing before his arrest, Mr Kivalu was played tape recordings of phone conversations with his wife and with formwork subcontractor Elias Taleb. Mr Taleb has alleged he paid Mr Kivalu $50,000 to win a contract to work on a Yarralumla building site.
Counsel assisting the commission, Jeremy Stoljar, put it to Mr Kivalu the recordings proved he was giving false evidence under oath.
Mr Kivalu denied this, saying the phone calls had been part of an elaborate ruse to pay back Mr Taleb who he said had been blackmailing him.
The commission has heard evidence from a number of tradesmen who alleged Mr Kivalu demanded cash, which they paid, in order to work in the Canberra market.
Mr Kivalu rejected claims he told Mr Taleb he could not work in the ACT unless his workers were CFMEU members.
He also denied he had a relationship with builders that would enable him to "influence them in any way concerning the appointment of subcontractors".