MNC IT company has given me an offer letter but now delaying my joining saying back ground verification not completed

One of the reputed India MNC IT company has given me an offer letter but now delaying my joining saying back ground verification not completed. Its a delay from their side but I have to undergo lot of stress as I do not have any offer in hand and I am relieved from my previous organization.
Please suggest what remedy I can follow or if i can take it legally.

Hi,
As they informed you that BGV is under process you can wait for some time. Because big Companies assign BGV process to a Vendor company and there might be more internal approval process which would have delayed your DOJ with them. Thinking of legal remedy before entering the Organization itself is not good.

Hi Lakshmi,
Thank you for the reply.
I understand that thinking of legal remedy is a not a good option but in spite of repeated e-mails, I have not got a single acknowledgement to my emails, which is very unprofessional.
The company can do the BGV concurrently.
What is the last remedy i have in my case.
Any thoughts or suggestion will be highly appreciated.
Thanks,
Probal