Internal auditor selection

We come across this clause in the Internal Audit procedure: 

[Job title] selects auditors in such a way as to ensure objectivity and impartiality, i.e. to avoid conflict of interest, because auditors are not allowed to audit their own work.

Given that our company is quite small, all employees are doing work relating to the ISO and therefore, an internal auditor may encounter something in the audit relating to their own work. Furthermore, the candidates that are able to assess all sides of the procedures (including the R&D technical side) are limited.

Does this mean that we have to hire an external auditor?