Dear Gajinder Singh,
Background Verification (BGV) is an important activity in the recruitment process. To do the BGV, with whom did you correspond? Was it with the HR department of the employee's previous company? We do not know what is the culture of that company, however, if the HR is non-communicative then you may write the send the BGV form by post. Address it to the MD of the company. Write a letter to them that they need not send the reply by post but just mark the answers and send the scanned copy.
Communication with the MD also remains unanswered then you need to take a call whether to do BGV or not. However, for the waiver of the BGV, obtain permission from the competent authority from your company.
By the way, if the employee's past company is not cooperating then you may obtain the declaration from the employee. For the contents of the declaration, you may
click here. This is my reply to some another post but the part of the contents are useful.
Thanks,
Dinesh Divekar