Electrician Steve Acheson has a pretty impressive CV and yet he just can't seem to get steady work. "I started as an apprentice in 1969 and I've worked on the channel tunnel, in the Middle East and around Europe. But in the last eight years I've not had one phone call from an agency," he says.
The only reason he can think of is that he's been blacklisted.
For 30 years it has been illegal to sack a worker for his or her union activities and it is commonly thought that blacklisting is also against the law. It was included in the 1999 Employment Relations Act, but in a discreet U-turn the government never formally brought in regulations to bring it to the statute book. Technically it remains legal.
In Christmas 2005 Acheson got a job on the site where a new hospital was being built in Manchester but was dismissed a couple of months later. He had already been involved in several industrial disputes and won a case where he was sacked because of his union membership. It was then that the issue of a blacklist was first raised. His fears were confirmed when the subcontractor who employed him on the hospital site let him go.
"Basically, I slipped through the net," he says. "Because it was Christmas they didn't carry out the usual checks. We were told there was not enough work but we suspected that there was a blacklist."
Unusually, his tribunal heard evidence from Alan Wainwright, a former manager in the construction industry, who testified that the blacklisting of trade union activists did go on. He said that private detective agencies sold lists of workers identified as troublemakers. In written evidence, Wainwright said: "I believe that certain UK construction companies and their mechanical and electrical subsidiaries operate a blacklist procedure to ensure certain electrical operatives do not gain employment on their projects."
The tribunal found for Acheson and two colleagues and this year they were awarded compensation. In its adjudication the tribunal said: "Disgraceful though it is, the tribunal concludes that a blacklist exists in relation to certain workers in the industry in which the claimants work and that the claimants are all on that blacklist."
Such findings are rare. One lawyer who has acted in many industrial tribunal cases says: "I'm absolutely convinced there are blacklists but the problem is proving it."
A spokesperson for Ucatt, the building union, says: "Blacklisting remains an issue in the construction industry. When companies refuse to hire skilled workers for no apparent reason, someone is pulling the strings in the background."
The view from employers could not be more different. A spokesman for the Construction Confederation says simply: "We're not aware of it existing. If unions have evidence of malpractice by an employer they need to share it. Blacklisting is not the practice of a good employer."
It seems like an issue of the past, a relic of the cold war era. Liverpool joiner John Winstanley had his career crushed because he was marked out as a trade union activist. Through the 1960s he was routinely refused jobs or had offers suddenly withdrawn.
"You become semi-institutionalised," he recalls. "You accept the fact you are only going to get work here and there. You go to a site with a genuine intention of getting work but in the end you can't keep facing the rejection. You make excuses to yourself and you walk away." Winstanley eventually left the joinery trade and went to work in local government.
The activities of private and public political vetting were explored in Blacklist, an 1988 book by Guardian journalists Richard Norton-Taylor and Mark Hollingsworth. They detailed organisations such as the Economic League, which held files on 30,000 "subversives" and supplied political vetting services to a number of companies.
The league was open about its mission to protect industry from left-wing "wreckers". However, its methods were secret and those targeted had no opportunity to question the information held on them. Parliamentary and media scrutiny eventually forced the league to close in 1993.
The chances of being screened before employment have vastly increased in recent years but, according to Jim O'Neill from Eurocom CI, that is because there are so many regulations which require companies to carry out pre-employment checks. It has nothing to do with people's personal opinions.
O'Neill says that his firm has not been asked to find out people's political views but that it is sometimes asked if someone regularly brings cases to industrial tribunals. "I can understand why they might be interested in that, but it's not something we can check," he says.
While the unions believe a casualised workforce makes it easier to target people perceived as troublemakers, employers say they need more information about potential recruits.
Michael Schuck is chief executive of Action Against Business Crime (AABC) which works with the British Retail Consortium. He says the issue is not about political preferences but the damage employers can suffer if references are uninformative or unreliable. The AABC has just launched the National Dismissal Register, which will hold details of individuals who have been dismissed or have left employment, even if only under investigation for acts of dishonesty. That might include theft, forgery or damaging company property. It will not, says Schuck, hold information on people's political opinions.
However, the register will not be backdated so will only be as accurate as the information supplied by subscriber companies who will be able to check it.
According to Schuck, the register has been scrutinised by the Information Commissioner's Office and he says there are numerous safeguards in place to make sure it is not abused. He adds that retailers, local authorities, transport companies, hotels and colleges have all expressed an interest in paying the £4,000 annual fee and joining the database.
But while such newer screening procedures claim to be open and transparent, it seems some old habits are still around. Electrician Colin Trousdale says secret lists of "troublemakers" still bedevil the construction industry - and he believes he is on one.
With 34 years' experience, Trousdale has held trusted roles and yet he has struggled to get a job for the last 18 months. He believes that speaking up for colleagues who were sacked has marked him out.
"I've had to change my address so that I didn't have a Manchester postcode because people saw the job application and thought I was one of the bolshie ones," he says. "All I did was speak up for some lads.
"People I know who have been blacklisted have suffered ill health as a result. They're under stress by virtue of the fact that they cannot get a job."
A spokesman for the Department for Business, Enterprise and Regulatory Reform explains that the government carried out a consultation and concluded that as blacklists didn't operate in the UK, legislation was unnecessary.
But Labour MP John McDonnell plans to pursue the issue and says it is "incomprehensible" why the government is refusing to bring forward the regulations. "Blacklisting is a covert, insidious employment practice," he says. "These regulations were meant to send out a message that it would not be tolerated under this government. Many trade unionists and our supporters will be disappointed at the government's failure to act."