The contractors were asked to dig a practice grave in an area of Easthill Cemetery in Frome, Somerset.

Mendip district council said that an “error in communication” led the trainees to dig up a green space of significant ecological value that campaigners are fighting to save from development.

When approached by a campaigner, the trio said they had been told to dig a hole there as part of their grave-digging education.

The land was formerly part of the park of East Hill House, once owned by the local MP Sir Henry Lopes, later Lord Ludlow. According to the friends’ group, the field is a “peerless, unspoilt gem in Frome’s natural crown” and “supports a myriad of wildlife in uniquely evolved habitats”, including endangered dormice.

Mendip district council said in a statement: “There are significant health and safety requirements associated with grave-digging, and extra training was essential. Previous training sessions have been completed at a number of council-owned cemeteries across the district. But burial services were unfortunately taking place in Mendip cemeteries. It was clearly inappropriate to conduct training at a location where a grieving family would be saying their goodbyes to a loved one. Given the short notice, Easthill was our only available location.”

A spokesman said that instruction was provided to the contractor to conduct the session on land within the boundaries of the cemetery but the instruction was “misunderstood”.

The spokesman added: “Having reviewed the situation and discussed the matter with all parties involved, I am satisfied this was simply a communication error with no malintent, albeit with significant consequences.”

He said that the space had “since been secured”.