Legal procedure & requirements to get death certificate

My father was expired on 7th january 2018 in a private trust hospital.as i am from a poor financial background i am able to pay to whole sum hospital bill.with the help of few social workers from the city we get the dead body and done funeral of my father at my hometome. As i approach to the nagar nigam office for issueing death certificate the nigam officers said that the record of death was not sent by the hospital,unless the hospital sends the record we (nigam officers) can not issue the death certificate. Please give advice to what to do now as the death certificate is most required and important document