Major construction firms which set up a "systematic blacklist" of construction workers appear to be continuing to avoid taking full responsibility for their actions, according to a damning report by MPs.
The Scottish Affairs Committee said it was "appalled" to discover that thousands of workers had their names put on the list, often for raising legitimate concerns over health and safety issues.
The list was drawn up by the Consulting Association, which was closed down in 2009 after being raided by the Information Commissioners Office (ICO). Unions are seeking compensation, arguing that those on the blacklist were denied work. Fewer than 10% of workers on the list are aware that they were included.
In an interim report, the committee said that while the blacklist was not initially illegal, it was always "morally indefensible", and the companies involved continued to use it after it had become illegal.
"The organisation set up to create, maintain and operate the blacklist - the Consulting Association (TCA) - appears to have been largely established by Sir Robert McAlpine Ltd, which also provided TCA's chairmen for eight of its 16 years of operation. Other major subscribers included Skanska and Balfour Beatty," said the MPs.
"Through the TCA the companies set up a structure which allowed them to submit names and information on workers they deemed to be unsuitable to a central list and to check prospective employees, or the employees of subcontractors on their sites, against this list.
"The emphasis throughout was on secrecy, with telephone access to sensitive information restricted to only a few, with the lists of names submitted destroyed at the end of each working day and no acknowledgement that such a system existed."
As part of its on-going inquiry, the committee appealed for evidence on whether blacklisting was still taking place, both within the construction industry and more widely, especially in Scotland, whether compensation should be paid and what penalties were appropriate for those firms and individuals who engaged in blacklisting.
Labour MP Ian Davidson, who chairs the committee, said: "We are appalled by what we have discovered during our committee hearings. The Consulting Association was an organised conspiracy by big construction firms, to discriminate against workers who raised legitimate grievances over health and safety and other industrial issues.
"This was an exercise run for the financial gain of the companies involved and those who benefited must be held accountable."