A GP clinic, as a private health service provider, cannot delete a patient’s medical file until a certain period of time passed. This period of time is seven years since the last service, or for the person under 18 years old until they reach 25 years old.
Should the patient insist, he/she needs to be politely referred to Health Complaints Commissioner in your State.
Source: Health Complaints Commissioner, https://hcc.vic.gov.au/public/health-records-individuals, last accessed 15/11/21