If a company is concerned with ethical sourcing and has concerns about issues such as...

Explanation

Completing Due Diligence checks will help guard against concerns about unethical business practices.

Not all companies will have a published Anti-Slavery policy- this is only required for large companies.

Known suppliers might have issues that you don't know about so you should always do due-diligence checks on everyone you work with

Formal tenders won't sort out ethical issues unless specifically addressed within the tender and strong contract management is put in place afterwards.