Unions Ucatt and Unite are the latest to pitch in launching class actions to coincide with today’s anti-blacklisting day of action.

General Union GMB started the legal action on behalf of 70 members against two contractors back in the Summer. Particulars of the claim will be served in the High Court at the end of this month.

Blacklisting protestors are targeting London sites of Sir Robert McAlpine and Laing O’Rourke including the Cheesegrater building.

Several other contractors’ sites spread around the country will also see demonstrations today.

The day of action against blacklisting is being staged to mark four years since 44 contractors were exposed for vetting workers against a secret database.

Ucatt said it was taking up the cases of workers who were blacklisted, suing for the misuse of private information and breach of confidence.

A spokesman for Ucatt said it would also commence legal action against an individual who held the position of chair of the Consulting Association and was a senior HR manager. His name is being withheld at this stage for legal reasons.

Unite has just issued its first tranche of five High Court proceedings against alleged blacklisters with 45 more High Court cases to follow.

The move follows a separate High Court claim against Sir Robert McAlpine by the rank-and-file Blacklist Support Group, which alleges the firm was involved in an unlawful conspiracy to amass a database of information against them.

The group claims McAlpine had the worst record of blacklisting, which is why it is being targeted in the legal action.

The conspiracy charge means McAlpine would also be responsible for the actions of more than 40 other contractors allegedly involved in the scandal.

Steve Murphy, General Secretary of Ucatt, said: “Blacklisting companies wilfully destroyed the lives of ordinary construction workers and acted as though they were above the law. Our legal action will ensure that the victims receive the justice they deserve.”

Last month eight contractors – Balfour Beatty, Carillion, Costain, Kier, Laing O’Rourke, Sir Robert McAlpine, Skanska UK and Vinci – set up a Construction Workers Compensation Scheme, which is offering compensation of up to £100,000 to worst affected victims of the blacklist.

Proposals also set a standard minimum payment of £1,000 for workers deemed to have suffered no loss from appearing on The Consulting Association database.

Workers agreeing to a deal will be required to drop any legal claims.