Is there any regulation or guidance if guarantors (secondary liability) could be reported to the credit bureau.

I'm in the middle - the Chief Credit Officer says they need to be because they need to be aware of all indebtedness.
The head of loans says that it is a secondary liability, and are not responsible for the individual payments, only in the event of default.

Thanks

You should not be reporting guarantors until your borrower defaults and you have made formal demand on them to honor the guarantee. They are not liable for the debt until that time.