The Health and Safety Executive has warned farmers not to use telehandler machinery to drive posts into the ground.
The call followed two fatal accidents in North Yorkshire at farms near Skipton and Thirsk.
In both accidents telehandler buckets came loose from the main telescopic arm and struck people who were underneath holding a post in place.
A 66-year-old woman died in Skipton while a 22-year-old man died in the Thirsk incident.
Investigations are yet to piece together the exact circumstances at each site, but the HSE and local police have stressed that telehandlers are not designed to drive posts into the ground.
“It is impossible to ensure that the post stays straight when a telehandler is used in this way, and further fatalities are possible if people continue to enter the danger zone beneath the bucket to provide manual assistance,” commented Gill Spurrier, HSE head of operations for Yorkshire and the Humber.
“If the bucket attachment is not properly engaged or becomes disengaged, the bucket can be dislodged by downward pressure on the post and may come loose completely – as happened at both Thirsk and Skipton.
“Both tragedies were easily avoidable, and we strongly encourage others not to work in this way.”
Chief inspector Nick Warnes, of North Yorkshire Police, added: “Workers have a duty to look after their own health and safety when carrying out work of this nature, and we are keen to avoid any more accidents like this.”