An independent report on the Maryhill plastics factory disaster describes the health and safety culture as "dangerously dysfunctional".
It says staff were "actively discouraged" from highlighting dangers and watchdogs were "faint-hearted".
The study published yesterday by academics at Stirling and Strathclyde universities using testimony from staff paints a picture of working life in the Glasgow factory and its sister companies in the months before the explosion that killed nine and injured 40 more in May 2004.
Last week, the owners of the factory, ICL Plastics and ICL Tech, were fined £400,000 for health and safety breaches that led to the accident.
The family-owned companies have accused the report's authors of "innuendo".
Professor Andrew Watterson, of the University of Stirling, one of the authors, said: "Everything from the company's health and safety culture, to oversight by the Health and Safety Executive and other regulatory agencies to the penalties laid down this week by the courts point to a system that gives a nod and a wink to the most negligent employers that they can risk lives with virtual impunity.
"The surprise is not that tragedy struck at ICL but that it didn't happen sooner."
Prof Watterson goes on: "Neither the Health and Safety Executive nor the firm took the action necessary to remedy problems over 20 years that had a clear potential for catastrophic failure," he said.
"This was a sick firm - workers regularly developed polymer fume fever' and former workers report a series of accidents, some requiring hospitalisation."
Prof Watterson's colleague, Professor Phil Taylor of Strathclyde University, said: "It is clear that working conditions in the plant were primitive.
"There appears to have been an absence of consultation - on either a formal formal or informal basis - with the workforce which was a reflection of the wider industrial relations culture and practices.
"Workers complained of heavy-handedness, arbitrariness and favouritism over questions of pay. Reports suggest that management had long been motivated by a hostility to trade unionism and a reluctance to respond to employees' concerns or to listen to their voices."
ICL said: "Meaningful comment is difficult until we are aware of the expert group's methodology. From their published comment, it appears to be anecdotal and characterised by innuendo."
The report's authors called for a full public inquiry and for tougher penalties for the owners of companies that breach health and safety rules. ICL and its owners, Campbell and Lorna Downie, have also backed a public inquiry. Their firms - including the trading division, Stockline, which gave the disaster its popular name - are still in business.
The Downies said: "In any public hearing, persons would have to justify their claims and be identified. Are the authors aware that the companies' health and safety practice was participative? We believe that may explain the remarkably few accidents in a 30-year history prior to the tragedy.
"While we have pled guilty to the criminal indictment we faced and have apologised unreservedly, we refute any suggestion that our working practices were persistently or routinely deficient or that we treat our employees unfairly."
Investigators found that the disaster was caused by a leaking gas pipe laid under ground in the late 1960s and left unchecked.
Campbell Downie, speaking to a Sunday newspaper, said: "It was quite obvious there had been a gas explosion, quite obvious the pipe had corroded and perfectly appropriate to plead guilty.
"The judge had a scale of wilful negligence at one end and inadvertence on the other. He put us on the low end of the scale."
Cause and effects
The explosion at the ICL Plastics factory on May 11, 2004, was the worst industrial accident on mainland Scotland for 40 years.
Nine people, including two company directors, were killed and about 40 injured. The four-storey building in Maryhill, Glasgow, was largely destroyed.
The cause of the explosion was shown to have been a gas pipe installed in the late 1960s which had become corroded and led to propane gas building up in a basement.
Gas from the pipe leeched into an underground room and was possibly ignited when a builder who rented the room for storage switched on an electric light.
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