The Health and Safety Executive (HSE) issued the warning after the most recent accident, in Wakefield, Yorkshire, where William Aveyard, 49, died after becoming trapped in machinery at Bezier's site.

Bezier said: "We express great sorrow at the loss of our colleague and we are currently working with the authorities to establish the cause of the accident."

A previous tragedy, 13 months ago at Terry Smith Group, West Drayton, London, mirrored the second in that during both accidents, hand-fed platen machines were in dwell mode – often used for replacing blanks.

"The power to the platen was not isolated before the intervention, and the safety devices did not prevent the platens closing," said HSE.

Hand-fed platens caused many serious incidents, it said. Bigger machines often led users to lean further into the platen area or climb onto the platen bed to intervene.

Bosses must use "robust safe intervention procedures" and consider when access was needed, how to minimise it and what to do when access was unavoidable.

Suitable procedures could include isolation and lock-off of the power supply. Employers must also ensure safe-intervention procedures were fully understood.

HSE said the two accidents were being investigated and refused to give further details. It has written to the BPIF.

Liz Cheetham, the BPIF's health, safety and environmental advisor, called on firms to immediately review risk assessments.

"They must ensure they have systems in place to cover access when making ready or following misfeeds."

Simon Lunken, BPIF head of health and safety, said: "All employers say 'it will never happen to us', but it does. It's all very well having procedures in place.

"But employers have a duty of care, and need assurances their staff are following those safety procedures."

To visit the HSE website, click here.