What is the key different between statutory audit and voluntary audit?

Statutory Auditors are appointed by the shareholders of the concerned company while the Internal Auditors are appointed by the company itself.
Statutory Auditors must be a chartered accountant while no such qualifications are prescribed for an Internal Auditor
Even though both of them do the same job, objectives specified for them are different. Statutory Auditors work for the shareholders and give their audit reports to them. Internal Auditors submit their audit reports to the company as they work for the sake of the company. Statutory Auditors can be removed only with the consent of the government while Internal Auditors can be removed by the company.