A newly hired internal auditor is performing an engagement that requires significant IT expertise that...

The principle from the IIA's Code of Ethics that would be violated by not informing the chief audit executive about the lack of required IT expertise is Competency. This principle requires that internal auditors apply the knowledge, skills, and experience needed in the performance of internal audit services. By deciding to perform an engagement without the necessary IT expertise, the auditor fails to meet the standards of competency expected.

The IIA's Code of Ethics, specifically the section on Competency.