Blacklisting firms in Wales to be barred from public sector contracts
Steps are to be taken to eradicate the illegal blacklisting of workers in Wales who are trade unionists or who raise health and safety concerns.
The Welsh government is to tell public sector bodies how to exclude companies that blacklist when recruiting staff.
Wales is the first UK country to try to stop the practice, where people are denied work because of their trade union membership or union activity.
In February, workers were found on an illegal building industry blacklist.
The Welsh government says the blacklist, which contained the names of more than 100 Welsh workers, is known to have been used by construction companies operating in Wales.
The UK government had considered legislation as early as 2003 but took no action because no hard evidence could be found that secret blacklists were being used.
But in 2009 construction companies were accused of subscribing to a database with details of workers' trade union activity and employment history.
Some 3,000 names of construction workers and their personal details were listed, alongside comments like militant, trade unionist and "not to be trusted".
The GMB union is taking legal action on behalf of some members while the TUC has called for a "day of action" in November.
In February, a BBC investigation found at least 111 workers from Wales were on the secret blacklist subscribed to by some of the UK's largest construction companies.
Most were unaware personal data was collated and used against them.
The Welsh government said it wants to send a clear message that blacklisting by firms bidding for contracts funded by taxpayers is inappropriate and illegal.
The Welsh government is advising public bodies that excluding firms from contracts must be justified by evidence - such as an admission of wrongdoing by the firm or a decision in a tribunal or court.
The guidance also states that "exclusion is not a means of punishing operators for past wrongdoing, but rather a means of putting right past wrongdoing and ensuring that it does not re-occur".
Finance Minster Jane Hutt said: "The use of blacklists is wholly unacceptable and I fully sympathise with the individuals and their families who have suffered a terrible injustice as a consequence of contractors engaging in this practice.
"Procurement is an important part of the overall policy toolkit of the Welsh government.
"Under no circumstances is it acceptable for any business in receipt of public procurement expenditure to use blacklists."
The public sector in Wales spends £4.2bn each year.
GMB national officer Justin Bowden told BBC Wales' Good Morning Wales programme that for more than a decade 40 of the largest construction companies in the UK organised a secret blacklist that contained thousands of names of individuals who worked in and around the industry.
"They shared those names and exchanged information about them and the net result of that was that 3,213 people were denied work," said Mr Bowden.
"In some cases they might get work for a short period of time, in other cases they perhaps (would) be offered a job and then told a couple of days later that they didn't get one."
Mr Bowden said those blacklisted had been unable to challenge what was put on the blacklists and "it had a huge effect on them and their families".
"The most common reason that people would be blacklisted for would be for raising health and safety concerns," he added.
He said people were blacklisted if they complained about asbestos in a workplace, unsafe guard rails or scaffold and even for overflowing toilets.
"But it could be for pretty much anything based on the opinion often of local supervisors about individuals," he added.