An internal auditor performed a consulting engagement last year which included assisting with management's design...

In the scenario where an internal auditor assisted with management's design of controls over the procurement function, the chief audit executive should plan an assurance engagement on the adequacy of the internal control system by assigning the engagement to another internal auditor on staff. This approach ensures that the evaluation of the controls is conducted with objectivity and independence, as the auditor who helped design the controls may have an inherent bias.

IIA Standards regarding objectivity and independence in assurance engagements.