The legal side of things is, at face value, a fairly simple case of being obliged to make sure that what you're using is suitable for purpose. I'm not aware of a specific regulation that says "you must have declarations", but without these one would have to wonder how you'd prove the point. Nonetheless I expect it is enforced in proportion to the scale and nature of the business - I'm pretty sure that a lot of smaller food companies and caterers wouldn't have these on file, but I don't recall ever seeing any of them challenged on it.
BRC is a bit more forthright about what it expects, but whether you'll be picked up on it depends on the auditor - there isn't time for them to check everything during each audit, but certainly over the years we've had to provide these for various direct and incidental food-contact materials such as gaskets, seals etc.
If the belts etc are direct food contact, or potentially food contact, then I'd agree with your supervisor that it's sensible to get the statements together for them.Go to the full post