The Department of Corrections says five prisoners got drunk on home-brew and used a skip filled with water as a swimming pool, before one of them attacked a prison guard.
The staff member was uninjured but one of the prisoners was so intoxicated he needed medical treatment.
The inmates were meant to be working in the engineering workshop at Christchurch Men's Prison, where their tasks included filling skips with water to check for holes.
Chief custodial officer Neil Beales said they were found climbing in and out of a skip on 29 October.
They were drunk on home-brew, which can be made from fermenting fruit and sugar.
"A staff member who came to assist was assaulted by a prisoner but no injuries were sustained. This matter has been referred to police," Mr Beales said.
The prisoner who required medical treatment returned to the site the next day.
Apart from the home-brew no other contraband was found.
All five prisoners were sacked from the workshop and three were moved to the Otago Corrections Facility.
"This is clearly unacceptable. Prisoners who take part in employment activities and industry training are expected to take this privilege and responsibility seriously," Mr Beales said.
"My team were asked to carry out an immediate review following this incident. This review remains ongoing."
He said immediate steps had been taken to prevent this happening again, including providing extra staff to supervise prisoners in the workshop.
In recent years the Department of Corrections has restricted the number of pieces of fruit that prisoners can purchase to prevent it from being stockpiled and turned into home-brew, as well as reducing access to containers and plastic bags that could be used to brew the concoction.