Is it mandatory for the Internal quality auditors to be certified by QMS certifying agency or in house training is good enough?

It is NOT mandatory.

However, Section 6.2.2 requires the organization to
a) Determine the necessary competence for personnel performing work affecting conformity to product requirements,
b) Where applicable, provide training or take other actions to achieve the necessary competence,
c) Evaluate the effectiveness of the actions taken,
d) Ensure that its personnel are aware of the relevance and importance of their activities and how they contribute to the achievement of the quality objectives, and
e) Maintain appropriate records of education, training, skills and experience.

Based on those requirements, if you train internally your auditors, you shall ask yourself:
– how to evaluate the effectiveness of the internal training,
– does your internal auditor have enough knowledge about the process to be audited and about the audit criteria.

Our experience also shows that a lot of internal auditors do write poor non-conformity statements and are not correctly trained on Root Cause Analysis, and Corrective Action Plans, and would approve poor actions plans.

Our Internal Auditor Training provides:
Audit Criteria Knowledge
Auditing Techniques and Non Conformity Redaction
Root Cause Analysis Workshop
Final Knowledge Examination.

www.symaconsulting.com