Supporters of blacklisted worker Frank Morris stopped traffic going into one of the main entrances to the Olympics site in Hackney, east London, on Thursday of last week.
Frank had been working for Daletech on the Media Centre being built by Skanska and Carillion for the last seven months.
He was dismissed after raising concerns about the sacking of another worker.
His sacking has raised suspicions that companies are continuing to blacklist trade unionists.
Steve Kelly, a blacklisted worker, told Socialist Worker, “We are identifying the companies operating the blacklist.
“One of the key blacklist companies is one of the main contractors at the Olympic site—Skanska.”