"There is an expression which says the fish rots from its head."
Ms Callaghan highlighted a series of health and safety incidents at Pike River that she claimed warranted significant further investigation.
They included an incident where loose rags and plastic were sucked up through the blades of an emergency helicopter called to a serious harm incident.
Another accident saw a worker injured by a rock fall caused by inadequate ground support.
Mine inspectors should have been very concerned that those incidents showed poor housekeeping and a lack of worker safety training, Ms Callaghan said.
She claimed the Department of Labour did not equip the inspectors to investigate complex matters of safety culture and did not give them easy access to legal advice.
"Departmental inspectors missed such a pattern of holes... They clearly identify a lot of well established error producing holes in the Department of Labour."
Ms Callaghan said the department had to improve its health and safety systems in the wake of the the Pike River disaster.
Not doing so would help lead to more deadly events, she said.
"It is to ignore the lessons New Zealand should already have learnt. The lessons from Erebus."
Ms Callaghan earlier pointed to evidence showing shift managers had cherry picked which health and safety incidents to report and investigate.
It was concerning to see some safety problems happened again and again within the mine, she said.
"The fact that they're repeated indicates to me... that either the action was not undertaken or it was not appropriate.
"You will see events stop being repeated."