It is not always necessary to instigate a parliamentary inquiry to bring the required facts of a matter to the fore. In some cases, a parliamentary investigation conducted by MPs will suffice. The difference between an "ordinary" investigation and a parliamentary inquiry is that a parliamentary committee of inquiry is empowered to hear witnesses under oath whereas an investigation committee is not. An initial investigation committee may come to the conclusion that a parliamentary inquiry is desirable.
Investigation committees and committees of inquiry both report to the House of Representatives. The House first discusses the report directly with the committee and subsequently debates the issue with the members of the Cabinet concerned. The ultimate purpose of this process is to identify lessons learnt and to take appropriate measures for the future.