The coroner looking into the deaths of the maintenance contractors in December 2010 recorded a narrative verdict on July 23. "It is our view that the death of each man was the result of a failure to adopt appropriate procedures."

James Bibby and Thomas Elmer were working on a conveyor, which started up automatically.

The court was told the men had not been shown how to isolate the power from the conveyor. "While there was a risk assessment carried out on the specific work undertaken by the men it appears this was not communicated to the men directly."

A spokesperson for Sonae told TTJ: "Sonae had a permit to work system in place, which, had it been followed, would have prevented the tragic accident. Training on general permit to work systems was given to the permit issuer which did contain all of the core components needed to operate Sonae’s permit to work system.

"It is now the role of the HSE to look at the findings of the inquest against the backdrop of their wider investigation and determine an outcome. The police completed its own investigation some time ago and as a result there are no criminal charges for the company or individuals to face that we are aware of."

The factory closed last year with the loss of 220 jobs after Sonae failed to gain permission for plans to rebuild after a fire.

Last week the High Court in Manchester set a trial date next year for a class action by 18,000 people alleging health issues related to plant emissions. The company said: "Sonae has admitted breach of duty, but has not admitted that the breach of duty has caused any resultant injury."