doubt about producing documents in job-consultancies

Dear Sir....I a resident of kerala . lately my friend told me that he has been asked by many job-consultancies to surrender his original 10th standard certificate but he refused.To his refusal they told him that they are taking the certificates as a security so that he will not refuse to give their ( consultancy ) service charge.I told him that he is not to give his original marks card because according to me....I feel they do not have the right to ask my friend to surrender his 10th standard certificate. Please guide me.....