The contractor responsible for the health of asylum seekers has been slugged more than $300,000 for problems relating to treatment of tuberculosis and other serious diseases in onshore detention, raising grave questions over the quality of care delivered to vulnerable people behind the wire.

A report by the Australian National Audit Office into onshore detention also found some detainees at severe risk of self-harm were being reviewed only once a fortnight, rather than every 24 hours as prescribed by official clinical guidelines.

It also found cost-cutting had led to changes to the way medication was distributed, creating the risk of prescribing and dispensing errors.

The findings cast into serious doubt assurances by the federal government and Department of Immigration and Border Protection that healthcare in both onshore and offshore detention meets community standards.