The CFMEU administrator sent corruption investigators away and later had to sack a top figure.
Two teams of investigators with experience in integrity were assembled to uncover corruption in the union but were disbanded.
A confidential source confirmed that the administrator, Mark Irving KC, failed to enact advice to seek more powers from the federal government to deal with wrongdoing.
One source said Irving was concerned that seeking more powers could risk reviving calls for the coalition's Australian Building and Construction Commission.
Former AFP officer Chris Craner was recruited to help investigate wrongdoing at the CFMEU.
Serious misconduct allegations remained untouched for months as suspected corrupt officials took key roles within the union.
Author's summary: CFMEU corruption investigation teams disbanded.