There is an old definition of a consultant as being someone who borrows your watch and then tells you what time it is. Sometimes even this can be a valuable service, but at other times it can simply be a rehashing of old news.
If you truly believe that this consultant does not know what he is doing, you should document the specific incidents that support this belief and discuss them with management. However, it is important to note that there is a consulting strategy in which the consultant tries to draw as much information as possible from the staff, purposely avoiding making any suggestions or recommendations during the process in order to avoid influencing the results. In such a case, it makes more sense to judge the consultant after he has presented his findings, analysis, and recommendations. If this consulting project is anywhere near completion, management may postpone acting on your concerns about him until they have his report in hand.
The larger issue is that the consultant did not establish his credibility with you and your associates at the outset, a time when he also should have clarified the steps, methodology, and objectives of the project. Perhaps the consultant needs a consultant.
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