Union activists are planning a series of demonstrations over blacklisting.
The GMB is targeting 63 construction managers during its Crocodile Tears campaign.
GMB national officer Justin Bowden said, “They might have thought they had got away scot-free, so shedding crocodile tears now for the systematic blacklisting of 3,213 building workers won’t wash.”
The Blacklist Support Group protested at Laing O’Rourke headquarters last week.
The latest round of action comes as Law firm Leigh Day resumed action in the High Court in London last Friday seeking compensation for blacklisted workers.
The case was adjourned until November.