When you notice, suspect or are aware of significant deficiencies in the work of another AICPA member you should seriously consider referring the matter to the Professional Ethics Division.
Prior to referral, consider your responsibilities under the "Confidential Client Information Rule" (section 1.700.001) of the Code of Professional Conduct if the member is affiliated with a client (for example, CFO of an audit client).
If you are unsure of the applicability of this rule, call the AICPA Ethics Hotline at 888.777.7077.