I work for a recruitment company, and as such we always ask new staff for a copy of their pass port to prove they are eligible to work in the uk. It is now one of the safest documents to use to identify a person.
If the member of staff does not possess one then we have to ask for several forms of ID before we can offer them work. This is to show that we have shown due diligence and we are not employing an illegal worker, or a person who is not eligible to work in the uk.
This has come in to force when the Government came under pressure after all the illegal immigrants found to be working.