An audit report has found serious flaws in the way the immigration department keeps tabs on visa holders breaching their conditions.
In 2014/15 the department granted more than 4.3 million visitor visas, 301,000 student visas and 300,000 temporary worker, humanitarian and migration visas.
It is responsible for ensuring visas are only granted to genuine applicants and they do not overstay or work illegally.
The Auditor-General found that while the department had a good idea of how many people overstayed, it did not have "comprehensive information about the nature and extent of visa holders' non-compliance with their visa conditions".
Figures released to the auditor found 15,550 people overstaying their visas by between five and 15 years and 17,370 overstaying by 15 years or more, out of a total of 61,980 overstayers in 2015.
The report found the department did not have an effective "risk and intelligence" function, following the abolition of its risk, fraud and integrity division in December 2014.
Despite these functions being dispersed to other areas of the department and the new Australian Border Force, "significant effort" would be needed to fix the problem.
The department was praised for its management of visa cancellations, but the audit found compliance field activities leading to cancellations were often "ad hoc" and were taking too long.
The audit recommendations were endorsed by the department.
