The GMB union has published a map to aid identification of its members held on the Consulting Association’s blacklist of construction workers.
GMB says legal firm Leigh Day are preparing litigation to get compensation for the 200 members it has identified.
It also hopes to prompt a further 300 people from the ICO list to identify their locations and contact the union.
The GMB, Ucatt, Unite and RMT unions have been provided data by the Information Commissioner’s Office to help identify which of their members may have been on TCA’s list.
Deputy Commissioner David Smith last month said the ICO had taken calls from 2,641 people who were concerned that they may have been on the list, 218 of whom were.
TCA was shut down following a raid in 2009, and the practice of blacklisting has since become illegal.
In its campaign letter the GMB said: “GMB is calling on councils not to award work to the companies that operated the blacklist until they compensate those they damaged.
“If you were a construction worker from one of those areas and as a trade union or health and safety activist were denied work for reasons you could not explain, get in touch so we can crosscheck the records.”
A spokesman for the ICO said: “The map GMB has produced has prompted more media coverage of the construction blacklist story, which prompts spikes in the number of people calling us about the issue.”
“That means more people are learning they’re on the list every week, something we all want to see.”
TCA’s list contains 3,213 names, once alias names and duplicates are excluded. GMB’s map shows where 2,554 of these people lived or worked.
GMB was unable to map 639 entries due to incomplete addresses and 20 further names in Scotland and Wales were unmapped.