Justice John Burns gave Halafihi Kimonu Kivalu, 39, a total suspended jail sentence of two years and nine months but placed him under a good behaviour bond until 2019 in the ACT Supreme Court on Thursday.

Kivalu was arrested after damning covert recordings were played to the trade unions royal commission last July, in which he told formwork subcontractor Elias Taleb to pay him so he could "get some people off your back".

Kivalu initially pleaded not guilty to two charges of blackmailing Mr Taleb and was set to fight the charges at trial, but later switched his pleas to guilty.

Justice Burns said he had given "particular consideration" to a letter from Kivalu's wife in imposing a suspended sentence for both counts of blackmail. She had described him as a "committed family man" who was "far from perfect" but was trying to turn his life around.

"Objectively. the offences you've pleaded guilty to are serious, they involve large sums of money and you were successful [in blackmailing the victim]," Justice Burns said.

"I take into account your pleas of guilty, which were not at the earliest opportunity but had degrees of remorse.

"I'm satisfied you have excellent prospects for rehabilitation and have rehabilitated yourself in this time."

Kivalu was handed a 21-month suspended jail sentence for the first count of blackmail, 18 months for the second count and the good behaviour bond was imposed until March 9, 2019.

Justice Burns also ordered Kivalu pay Mr Taleb reparations of $70,000.

Kivalu blackmailed Mr Taleb over work at a Yarralumla residential development between February 2012 and June 2013 and an apartment complex development in Braddon between September 2013 and January 2014.

Kivalu – a Construction, Forestry, Mining and Energy Union organiser between 2010 and November 2014 – made it clear to Mr Taleb that if he did not pay him $50,000 to secure the Yarralumla site a competitor would pay and the work would go to them.

Mr Taleb believed he needed to make the payments to keep the CFMEU from disrupting work at his sites.

Kivalu, who is a former president of the ALP's Dickson-Morning sub-branch in Canberra, was present when the CFMEU shut down Mr Taleb's Yarralumla site in late 2013.

According to court documents, he later told Mr Taleb: "Look, I sorted it, but you are going to have to give me some money. Let's do the deal."

Mr Taleb then paid Kivalu $20,000, a police statement of facts said.