The Attorney-General's Department has rejected calls from legal experts and privacy advocates for greater oversight on proposed data retention legislation, saying that obtaining a warrant for every metadata request would be an onerous burden on law enforcement and security agencies that could see criminals going undetected.

The AGD has published its submission [PDF] to the Parliamentary Joint Committee on Intelligence and Security inquiry into data retention, warning that the bill's passage is necessary to ensure guaranteed access to telecommunications data into the future .

The submission argues that the data retained (such as the source, destination and time of communications) is a necessary tool in criminal investigations and security operations. Further, the Department contests that retaining and using metadata is "one of the least privacy intrusive investigative tools available" to law enforcement and national security agencies, compared to physical surveillance and search powers.

But despite the importance of such data to investigations, the AGD said a warrant should not be required to access this information, and that the warrant application process would be a time-consuming impediment for police and security.

Warrant applications are resource intensive, and can take days, if not weeks, to prepare and complete. Attorney-General's Department submission on data retention

"The benefits of introducing a warrant regime would be outweighed by the impact on agencies' ability to combat serious crime and protect public safety," the submission reads. "Warrant applications are resource intensive, and can take days, if not weeks, to prepare and complete."

The Department warned that any delays for law enforcement and security agencies "would seriously harm their ability to investigate crimes or threats to national security".

In arguing this case, the AGD raised the spectre of serious criminal activity and warned of further reductions in police powers to target criminals, citing examples of unsuccessful attempts to prosecute paedophilia and sexual offenses because of lack of access to metadata in the past.

It is not the first time the Attorney-General's Department has pushed back against the "disproportionate impact" of warrant schemes. The Department previously argued [PDF] that agencies issuing warrants "would be unable to cope with the large number of new warrant applications that would be required" while those applying for warrants would be constrained in obtaining "the preliminary information required to support their warrant".

The AGD also argued that warrants are typically reserved for the most intrusive law enforcement powers, and that "non-warranted access to information is a normal part of any law enforcement framework".

Concerns about oversight on data retention

However, legal experts have rejected the AGD's calls for warrantless access. The Law Institute of Victoria submission to the inquiry [PDF] said claims that data retention is less intrusive than methods such as surveillance are "no longer valid" considering the complexity of internet-related metadata.

"This requirement [of obtaining a warrant] is not a disproportionate burden on law enforcement agencies given the intrusive nature of the power," the Institute argued.

The AGD has argued that the Data Retention Bill requires "independent oversight" of metadata access, saying this is "preferable" to a system that requires warrants.

"Independent oversight has a very similar psychological effect to a warrant process," the Department submission reads. "Knowing that an agency's access to data is going to be scrutinised by an independent overseer is a strong deterrent against non-compliance or misconduct."

However, the Australian Human Rights Commission has criticised the independent oversight written into the Bill (from both the Commonwealth Ombudsman and from a proposed review to occur three years after data retention is introduced), saying these measures only offer scrutiny of metadata access after the fact.

"While these safeguards are important checks on the scheme, they are all directed at reviewing access powers after they have been exercised," the Commission wrote in its submission on data retention [PDF].

"The Commission considers that a warrant or authorisation system for access to retained data by a court or administrative body provides a more effective safeguard to ensure that the right to privacy is only limited where strictly necessary."

The Parliamentary Joint Committee on Intelligence and Security is set to hold another public hearing on the Data Retention Bill on January 29.