Three Christchurch prisoners have been moved to Otago - for throwing a drunken pool party

Christchurch Men's Prison has had to step up supervision in its industry training workshops after the incident in late October.

Chief Custodial Officer Neil Beales says the prisoners were in an engineering workshop refurbishing waste skips - including filling them with water to make sure they had no leaks.

He says five of them were found drunk on homebrew alcohol jumping in and out of a skip.

Beales says one staff member was assaulted when they stepped in - but sustained no injuries.

One prisoner also had to be treated in hospital for intoxication.