Unite is seeking compensation on behalf of more than 70 construction workers who were blacklisted by the Consulting Association. The company's secret database containing the details of more than 3,200 building workers had been used by some of the UK's largest construction firms to identify potential "troublemakers", including those who reported safety failings, and deny them work.
The new legal action for unlawful conspiracy is against former chairs of the Consulting Association: Cullum McAlpine and David Cochrane, both of whom were employed by Sir Robert McAlpine; Danny O'Sullivan, a former Kier employee; and Stephen Quant, who was employed by Skanska UK.
It is part of a wider case against those companies and nine others, including Balfour Beatty Construction, Carillion Construction and Costain, alleging breach of privacy, defamation and Data Protection Act offences.
Last year Unite secured £10.4m compensation for 256 formerly blacklisted workers. The Information Commissioner's Office closed down the Consulting Association in 2009 and fined its operator, Ian Kerr, £5,000 after it uncovered the blacklist.
Unite assistant general secretary for legal affairs Howard Beckett said: "Since 2009 the individuals who were the controlling minds behind the systematic blacklisting of workers have sought to avoid taking responsibility for their actions. The workers who had their lives ruined deserve to see the leading blacklisters in court."
In September a group of MPs called for Sir Robert McAlpine to be stripped of its contract to restore the Elizabeth Tower and Big Ben in London's Houses of Parliament due to its blacklisting history.
The construction and civil engineering giant's chief executive Paul Hamer responded in a letter which claimed blacklisting "has no place now or in the future" at the company, which is committed to a "zero-tolerance policy towards blacklisting, illegal or unfair recruitment practices". He added: "I am pleased to confirm to Sir Robert McAlpine complies fully with all legislation to prevent blacklisting and is committed to fair and transparent recruitment."