It was revealed last month that the ACT branch of the Australian Federal Police had illegally accessed metadata more than 3000 times in 2015, including in one case where the data may have been used in a prosecution.

Metadata includes information like the time of phone calls and text messages and who they are to. It also includes who a phone number is registered to, and can include location information.

Telcos must retain metadata for two years, a period that parliamentary inquiry is considering extending.

Mr Dutton said the federal government had no responsibility for sanctioning ACT Policing, as the branch was under the remit of the "local council government" - the ACT government.

But the territory government is prevented from making laws about ACT Policing under the Self-Government Act.

The same law prevents the new ACT Integrity Commission investigating corruption complaints against ACT Policing.

Prime Minister Scott Morrison in March ruled out changing the law to give the integrity commissioner jurisdiction over ACT Policing.

"Any delineation between ACT Policing and the broader AFP would be legally and practically problematic," Mr Morrison said.

In a letter to Attorney-General Christian Porter this week, Mr Barr said Mr Dutton's comments highlighted the need for oversight of the police to be clarified.

"Mr Dutton stated that the Commonwealth takes no responsibility for the actions of ACT Policing and he viewed its operations as falling within the remit of the ACT government 'as we see in other states and territories'," Mr Barr wrote.

"It is unacceptable the ACT government should have responsibility yet limited oversight capacity."

A spokesman for Mr Porter said they had not received Mr Barr's letter, but deferred to the Prime Minister's previous comments on the matter.