Builders are to take their fight against blacklisting to Strasbourg, Ucatt confirmed today.
The construction union lodged a test case at the European Court of Human Rights on behalf of one of its members, arguing that the government's failure to ban blacklisting violated workers' human rights.
The issue came to the fore after Britain's data watchdog raided the offices of the Consulting Association in 2009.
The Information Commissioner's Office (ICO) found that the firm kept a database, used by 40 major construction companies, stuffed with information on more than 3,000 workers.
Blacklisting was meant to be outlawed in 1999 by the Employment Relations Act, but the regulations weren't into force.
But the evidence dug up by the ICO investigation forced the previous Labour government to introduce new rules in 2010 before the general election.
But unions and campaigners say the new legislation does not go far enough and effectively gives companies the green light to blacklist workers.
And Ucatt argues that the Con-Dem coalition has done nothing to stop it.
The union's case at Strasbourg argues that this breaches Article 11, freedom of association, and Article 14, anti-discrimination, of the European Convention on Human Rights.
If successful, the case would set a precedent and could compel the government to close existing legal loopholes.
The union expects the court to contact the government about the matter by the end of the year - the first stage of what is a potentially long legal process.
Ucatt general secretary Steve Murphy said: "The lives of construction workers and their families were wrecked by blacklisting.
"Ucatt remains absolutely committed to winning justice for blacklisted workers. That is why we are taking this battle to Europe."
Steve Cottingham, a partner at OH Parsons, who has represented blacklisted Ucatt members, said: "Both the government and judicial system have failed to provide justice for blacklisted workers.
"The only other legal recourse was to lodge a case with the European Court of Human Rights."