Labour wants the Corrections Department to release its report into problems at Auckland's Mt Eden prison as soon as possible.
Corrections have finished the first draft of the report into the Serco-run facility and evidence of prisoner fight-clubs.
MP Kelvin Davis says some of the report findings may be impossible to hide.
"I think there's some things that they just can't possibly hide, and they have got to spend time working out their lines to make sure that they can put the negative story into the best frame that they possibly can."
Mr Davis suspects the Government is planning the best time to release the final report, to minimise the damage caused.