This sounds familiar.....at our last audit I was instructed to amend our internal auditing system and frequency, as it did not fall in line with how the auditors preferred it to be.
Some of our procedures and processes are more critical than others and are audited more frequently - I was informed that our certification body preferred ALL of our procedures to follow this frequency.
As they are auditing to a standard and this does not dictate actual audit frequencies they were out of order - but would not accept it. After a lengthy debate I conceded that they should raise it as a non-conformance, but unfortunately they conceded that they could not raise it as a non-conformance as we were within the boundaries of what the standard dictated and only failed against what they wanted -
In the end it was raised as an observation.
Surely there is enough that we must adhere to, to comply with all of the standards without auditors feeling the need to try and impose more?
My opinion is that if you are comfortable that you meet with the requirements of whatever standard is being audited - stand your ground.