Sixty activists have vented their anger during a protest over the scandal of blacklisted workers.
The demonstrators at the Alder Hey Hospital building site in Liverpool want to highlight what they claim is the continued anti-union stance, and denial of facilities for trade unionists, of the site's main contractor, Laing O'Rourke.
It is one of eight major construction companies which are to compensate workers whose names were on a secret industry blacklist of 3,200 men, exposed after years of campaigning by unions.
Workers on the blacklist claimed they were denied work, often for merely raising legitimate concerns about health and safety on building sites.
Legal action is being taken on behalf of some of those on the list, with the case in the High Court on November 29.
Saturday's protest was called by the Blacklist Support Group, which says Laing O'Rourke has refused to negotiate with construction unions over rates of pay or safety and has denied union officials access to the site to speak to workers.
Steve Acheson, a blacklisted electrician and chair of the Blacklist Support Group, said: "Laing O'Rourke may pretend they have turned over a new leaf by their involvement in the compensation scheme but they show their true colours every day by their anti-union actions on building sites across the UK.
"They appear to be pathologically predisposed to victimise workers prepared to stand up for basic rights such as safe conditions or wages."
The construction unions Unite, Ucatt and GMB all had members at the protest. No one from Laing O'Rourke was available for comment.
The protest came a day after the announcement of the death of a construction worker on the Laing O'Rourke Francis Crick medical research centre project in London's King's Cross.
Unite assistant general secretary Gail Cartmail said: "This is a harsh reminder of the importance of high standards of health and safety in an industry that is extremely dangerous.
"Trade unions have a role to play in maintaining safe working environments but Laing O'Rourke has bizarrely banned Unite officials from their sites."
The TUC is organising a national day of action on November 20 over the blacklisting, when the 'Cheesegrater' building under construction in central London, another Laing O'Rourke site, will be targeted. Unions want a Leveson-style inquiry into the scandal.