Two brothers Thomas and Dan Hazelton, Peter Johnson and Adam Taylor died on 21 January 2011 after a steel cage “folded like a picnic table” crushing them.

The Suffolk men, working for family groundworks contractor Hazegood Construction, had been constructing a steel cage to reinforce the concrete foundations of a high pressure test bay at Claxton Engineering in Great Yarmouth.

They were within the cage, which was inside a 2m deep trench the length of a tennis court, and were fixing steel above their heads when it collapsed.

A total of 39 tonnes of steel and 330 tonnes of concrete would have been used in the completed structure.

The BBC reported that Coroner Jacqueline Lake directed the jury that accidental death was the only verdict open to them.

She said they must not apportion any blame or reach a verdict that may cause either civil or criminal proceedings.

Hazegood Construction director Matthew Hazleton, the brother of two of the men who died, said his company had struggled to find work as a result of the damage to its reputation.

He said a decision would be made in the future by him and his fellow director Neil Gooderham about whether to continue running the business.

A statement from the families of the four men who died said: “The evidence clearly showed that Dan, Tom, Peter and Adam were conscientious and skilled workers and no concerns were raised about the steelwork they were doing.

“We hope the Health and Safety Executive will take appropriate action against those responsible so justice is done, and that lessons will be learned to ensure such a terrible tragedy never happens again.

“We would like to thank those who tried to rescue the men and for all the support we’ve received over the last three years.”

Jon Elven, of the HSE, said: “The HSE will now review the evidence in light of the inquest and decide about whether further criminal proceedings are appropriate, and will announce any decision in relation to this in due course. Meanwhile our thoughts remain with the families of the deceased.”