The Office of the Australian Information Commissioner announced the investigation on Friday evening but provided no timeline.

In its announcement, the commissioner pointed to the department's tardy compliance, saying it responded to under half of all FOI requests within the required time in 2018/19.

The Department of Home Affairs oversees Australia's immigration, border control, federal police and intelligence agencies.

OAIC Commissioner Angelene Falk told a Senate estimates committee earlier in the week on Tuesday that her office - which also protects Australian's privacy rights - needed more resources.

Ms Falk said of nearly 39,000 FOI requests made to government agencies in 2018/19, only 52 per cent were granted in full.

"What the statistics indicate is that, in a number of cases, agencies are applying exemptions in relation to the requests that are made," Ms Falk said.

Labor senator Kim Carr, in the same hearing, referred to Home Affairs' low compliance as part of a "culture of lawlessness" in the department.

When asked by Senator Carr which department was the worst for compliance, Ms Falk pointed to Home Affairs, saying "timeliness had been an issue with that department".

Of 734 FOI requests to Home Affairs for non-personal information that financial year, 56 per cent were not handled within the required timeline.

Government agencies get 30 days to respond to requests but can be granted extra time depending on circumstances.

"The OAIC has received a number of FOI complaints and review applications related to the department's compliance with statutory timeframes," the commissioner's office said in Friday's statement.

"One of the objects of the FOI Act is to facilitate and promote public access to information, promptly and at the lowest reasonable cost."

Australian Associated Press