Halafihi Kimonu Kivalu, 39, 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 blackmailed Mr Taleb in relation to 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.

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.

He faced the ACT Supreme Court for sentencing proceedings on Wednesday.

Defence barrister James Sabharwal said Kivalu, who had been his family's main breadwinner, would likely find it difficult to obtain work in the wake of publicity surrounding the charges.

He said Kivalu was held in high esteem in the Pacific Islander community in Canberra and Queanbeyan.

Mr Sabarhwa–l asked Justice Burns to impose a suspended jail sentence and order Kivalu to undertake unpaid community service work.

Crown prosecutor Anthony Williamson urged Justice Burns to take into account the fact Kivalu had successfully obtained a significant amount of money from Mr Taleb, the two-year timeframe the blackmail took place, and the "distressing" position he put the victim in.

He said blackmail was a serious crime that was often difficult to detect, given the reluctance of victims to come forward.

On the rare occasion blackmail charges were brought before the courts, there was a need for individualised justice to send a strong message of deterrence to the community, Mr Williamson said.

"The court should impose a sentence that would compel any other rogue union organisers, or or anyone for that matter, to think twice before they consider engaging in that conduct."

But Mr Williamson agreed with the defence's suggestion that Kivalu's offending should be dealt with by way of a suspended sentence and volunteer community work.

Justice Burns will hand down his sentence next month.

Apology: An earlier version of this story carried an incorrect photo of Kivalu's lawyer Toni Tu'ulakitau, instead of Kivalu. The Canberra Times apologises to Mr Tu'ulakitau for any harm caused by the error.