Councils and other public bodies are being urged to stop giving work to companies who were found to be involved in blacklisting construction workers.
Seven years ago when the Information Commissioner's Office seized a Consulting Association database of 3,213 construction workers and environmental activists, used by 44 companies to vet new recruits and keep out of employment trade union and health and safety activists.
It has cost leading building firms tens of millions of pounds after an out of court settlement last month in which about £50m was paid out in compensation to 771 workers.
Justin Bowden, national officer of the GMB union, said: 'Having established that the construction companies lied and denied before finally caving in and paying their way out of a hugely embarrassing trial, it is time now for local authorities and other public bodies to stand by their promises to stop using blacklisting companies.
'GMB will be ensuring all local authorities are fully informed about their obligations in relation to procurement and blacklisting companies, and where taxpayers' money is spent.'
Balfour Beatty, Carillion, Costain, Kier, Laing O'Rourke, Sir Robert McAlpine, Skanska UK and Vinci said last month they had settled the litigation, bringing an end to all legal claims.
