If the skills and competencies are not present within the internal audit activity to complete...

If the internal audit activity lacks the necessary skills and competencies to complete an ad-hoc assurance engagement, the most appropriate and professional action is to politely decline the engagement due to a lack of qualified staff. This decision upholds the IIA's standards on professional proficiency and due professional care.

The Institute of Internal Auditors (IIA) - International Standards for the Professional Practice of Internal Auditing.