Why does RecruitAGraduate not accept written employment references?

Why does RecruitAGraduate not accept written employment references? 

Sadly to the number of fraudulent written employment references that get submitted, we no longer accept written references. However, if you get invited to an interview and would like to submit a further written reference, this can be emailed to your recruiter with the contact details of the referee. If the referee can not be contacted, the reference will not be used.

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