More than 100 North East workers were on construction blacklist
An agreed statement announcing the settlement of litigation between members of the Ucatt, Unite and GMB unions and several leading construction firms was read out at the High Court.
The packed courtroom erupted when counsel for the companies, Andrew Caldecott QC, rose to offer their "sincere and unreserved apologies" for the damage caused.
Mr Caldecott said appropriate sums by way of damages and costs had been agreed, but no figures were revealed in court.
Earlier this week, Unite announced it had reached a settlement which would see 256 workers receive more than Â£10million in compensation.
Unite said payouts could range from Â£25,000 to Â£200,000 per claimant, depending on such factors as the loss of income and the seriousness of the defamation.
The GMB, which reached a settlement last month, said it understands the total value of compensation in the case was around Â£75million for 771 claimants, with legal costs on both sides estimated at Â£25million.
Blacklisting came to light in 2009 when the Information Commissioner's Office seized a Consulting Association database of 3,213 construction workers and environmental activists used by 44 companies to vet new recruits and keep trade union and health and safety activists out of employment.
Some of those on the list said they were denied work, while a handful moved abroad because they could not find jobs in this country.
Figures released today by the GMB showed that 130 workers in the North East were found to have been blacklisted - 69 in Tyne and Wear, 43 in Redcar and Cleveland, 11 in Durham and seven in Northumberland.
A statement on behalf of Balfour Beatty, Carillion, Costain, Kier, Laing O'Rourke, Sir Robert McAlpine, Skanska UK and Vinci PLC - announcing the settlement of the litigation at the start of the week - said that in October 2015 they acknowledged the system was unlawful in various respects and made a full public apology.
"These construction companies wish to draw a line under this matter and continue to work together with the trade unions at national, regional and site level to ensure that the modern UK construction industry provides the highest standards of employment and HR practice for its workforce."
Mr Caldecott said: "The defendants apologise as providers of any information and for the loss of employment suffered as a result of communication of information during the operation of the Consulting Association.
"They also apologise for the anxiety and hurt to feelings caused as a result."
GMB legal director Maria Ludkin said: "Despite years of denials, today the greedy goliaths have been forced to apologise and account for their unlawful blacklisting."