Two prisoners who climbed on to a jail's roof in hot weather were offered sunscreen by staff.
The pair turned down the offer during the incident at Dartmoor prison in Devon on June 19.
It is not clear how the inmates managed to get on to the roof or which building on the site in Princetown was involved.
The Ministry of Justice (MoJ) said the offer of sun lotion was in line with health and safety rules.
But John Hancock, from the Prison Officers' Association in the South West, described it as "absolutely ludicrous".
Mr Hancock told the BBC: "They shouldn't have been up there in the first place.
"It's only going to encourage other inmates to get on the roofs and expect sun cream, and possibly cold drinks and ice creams as well."
Dartmoor prison, which is currently able to hold 659 inmates, was originally built to hold French and American prisoners of war in 1809.
An MoJ spokeswoman said: "On Thursday 19 June, there was an incident at height at HMP Dartmoor involving two prisoners.
"The incident was successfully resolved by negotiation at 4.28pm. No staff or prisoners were injured."