What Are The Disadvantages Of Auditing?

It is not fool-proof and is based on a statistical testing of items that may not have the problems or information needed to discover false or illegal activities. Since not everything is tested or reviewed there is potential for deception. It is also very costly and the people that hire the auditors and pay them are the one's being audited. As such the auditors while having a responsibility to the public for reporting are also depending on the client that they are making the assessment to pay them.

Speaking from experience in a large state agency, the one negative aspect of auditing that I saw was overzealous auditors trying to control management/engineering.  Instead of ensuring that we were doing our jobs, they tried to do some of their own goofy engineering under the guise of cutting costs.  It came to a head because they were causing extra work for us and themselves.
In later years, the auditors disappeared just about agency wide, and the quality of records went down the toilet.  Nobody had to ever justify decisions and that knowledge greatly affected the care rendered in decision making.
Of the two examples I have given, the lack of audits, in my opinion was the greatest auditing mistake I had ever seen until the great banking/investment debaucle of the early 2000's.  At least, there was not unpunished theft and gross self-profit and fraud in my agency, just higher cost to the tax payers.