The Immigration Department has been accused of unlawfully and inappropriately conducting personal searches at international airports and breaching coercive powers.

Key points: ANAO report raises concerns over the department's ability to ensure officials legally question, detain, search and arrest people

ANAO report raises concerns over the department's ability to ensure officials legally question, detain, search and arrest people The report claims officers "routinely questioned people without documenting their legal authority to do so"

The report claims officers "routinely questioned people without documenting their legal authority to do so" Department secretary Michael Pezzulo dismisses claims, criticises "loose terminology"

But the allegations, contained in the latest Australian National Audit Office (ANAO) report criticising the Government department, have been rejected as "unworldly" by department secretary Michael Pezzullo.

The audit raised concerns about the department's ability to ensure officials legally question, detain and arrest people, or search vehicles and properties.

"Some personal searches of passengers at international airports examined by the ANAO were unlawful or inappropriate, indicating weaknesses in the control framework," the audit said.

The report found "significantly more work" needed to be done to provide assurances that these search powers — which include "frisking" at airport security gates — were being used appropriately.

The audit found a number of property searches exceeded the scope of warrants, and officers "routinely questioned people without documenting their legal authority to do so".

It found the department had not provided officers with "adequate instructions and guidance" for exercising coercive powers.

But Mr Pezzullo criticised the report and said some of the incidents could be categorised as "inadvertent" or "maladministration" rather than flagrant breaches of power.

"The analysis, and I have to be very frank and candid with this committee, is not necessarily keeping with the standards that we would expect to see in an audit report," he told a Senate estimates hearing.

"Loose terminology such as the use of coercive powers being point of issue.

"We dispute fundamentally what we think is erroneous reference to coercive powers."

Mr Pezzullo criticised a number of recent reports by the audit office, including claims more than $1 billion was spent over the last four years without proper authorisation.

"Regrettably, it's becoming a bit of a reoccurring pattern with the audit office," he said.

"We are engaged with them very civilly, very professionally, about how we can work with them and narrow some of these methodological and factual differences."