Australian Federal Police will not lay any charges against News Corp journalist Annika Smethurst after investigating leaked documents she had used in an article.
Smethurst has been under investigation since publishing a story in 2018 detailing secret plans to expand the powers of an Australian spy agency.
AFP Deputy Commissioner Ian McCartney has confirmed no charges will be laid and will address the media in Canberra on Wednesday afternoon.
He said there was insufficient evidence to prosecute, but confirmed police had looked at material collected in the raid on Smethurst's home.
Attorney-General Christian Porter said he does not know why the investigation took so long to resolve.
Australian Federal Police Deputy Commissioner Investigations Ian McCartney speaks to the media in Canberra. Source: AAP
"I share a level of frustration," Mr Porter said in Perth on Wednesday.
"But these are decisions that quite properly in our system are made independent of ministers in executive government."
Mr McCartney said it had been a complex investigation into a potentially serious breach of national security laws.
"We did our job, we investigated," he told reporters.
"There was insufficient evidence to show the path of the (leaked) document, where it came from, and who it went to."
He pointed to the High Court case on the legality of the warrant used to raid Smethurst's home as to why the decision to drop charges was delayed.
Ms Smethurst's Canberra apartment was raided in June 2019, sparking a major debate about press freedom in Australia.
Officers seized information from the reporter's phone
Ms Smethurst challenged the raid in the High Court, arguing the search warrant was poorly drafted and too vague.
The full bench found in her favour last month, declaring the warrant invalid but allowing AFP to keep the seized materials.
The AFP sought legal advice on what to do with the evidence after the decision was handed down.
Mr McCartney said after reviewing the seized materials police decided they didn't have enough evidence to continue investigating.
In October last year, the AFP flagged an external review of the agency's policies and guidelines around sensitive investigations.
Mr McCartney said the review had since defined what could count as a "sensitive" investigation, including those involving journalists or politicians, with clear guidelines now in place.
"I'm very supportive of the concept of press freedoms in terms of shining a spotlight ... on some of the positive work the AFP does," he said.
The Media, Entertainment and Arts Alliance's Marcus Strom said that despite the charges being dropped, laws criminalising journalism remained.
"It shows how Australia's national security laws are being misused in order to criminalise legitimate public interest journalism," he said.
He said unless major reforms took place, including the right for media companies to contest warrants, Australians will be denied their right to know.
The Law Council of Australia also said concerns remain over the ongoing "vulnerability" of public interest journalism to investigations by law enforcement and security agencies.
"The law continues to leave journalists and media organisations exposed to possible police investigation and prosecution," President Pauline Wright said.
The Law Council said Australian "secrecy laws" do not contain adequate safeguards for journalists to report on matters of public importance.
Mr McCartney could not say when a separate AFP investigation involving two ABC reporters would be finalised.
"We are moving as expeditiously as we can," he said.
ABC News director Gaven Morris wrote on Twitter it was also a good time to call off the investigation into the ABC reporters.
Police last year raided the ABC's central Sydney head office following 2017 news reports based on leaked Defence Department papers revealing Australian defence personnel may have committed war crimes in Afghanistan.
It is understood the ABC has repeatedly sought meetings with the AFP, without success.
