Only one construction worker in Northern Ireland out of 3,200 across the UK has been blacklisted, according to the GMB union.
A map showing the full extent of the "scandal" of workers blacklisted in the construction industry was drawn up as part of a campaign for compensation.
The GMB union said it hoped its map would help identify the 3,200 workers whose names were on the list, which was drawn up by the Consulting Association.
The existence of the list was revealed after a raid by the Information Commissioner's Office in 2009, which led to the Consulting Association being closed down.
MPs on the Scottish Affairs Committee have launched an inquiry into blacklisting, and the issue was debated last week in the Commons.
Shadow business secretary Chuka Umunna said what had happened was "nothing short of a national scandal".
Unions claimed workers' names were included if they had raised health and safety issues, or were union activists, and it denied them future employment.