Cameron Gill was named in court documents by the federal police as the alleged leaker of documents to journalist Annika Smethurst, and both Mr Gill and Ms Smethurst had their houses raided as part of the investigation. Today it was confirmed neither would face charges, more than two years after the story was first published.

Mr Gill's lawyer Michael Kukulies-Smith lambasted the police in a statement on Wednesday afternoon, after Mr Gill was also told the investigation had finished. He said Mr Gill had been cooperating with the police, but they still decided to raid his home in September last year, an action which revealed his identity in the media, causing him to be reported as a suspect.

"Mr Gill is disappointed that despite repeated opportunities the Australian Federal Police have chosen not to apologise and remedy their actions that have severely damaged his professional reputation and personal health," the statement said.

Federal Police Deputy Commissioner Ian McCartney said there was insufficient evidence to continue with the case, which surrounded the leaking of Top Secret documents to the journalist.

"We follow the evidence. In this case, there was insufficient evidence to show the path of the document, where it came from, and who it went to. Our decision was based on in effect the sufficiency of evidence."

The decision was made after the High Court ruled the raid on Ms Smethurst's Canberra apartment last year was invalid, but no orders were made for the destruction of the evidence.

Ms Smethurst had been under investigation since publishing a story in 2018 detailing a proposal to allow the Australian Signals Directorate to spy on citizens without a warrant.

Attorney-General Christian Porter does not know why the investigation took so long.

"I share a level of frustration as to how it took so long to resolve," 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."

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 after rummaging through her drawers and cupboards for several hours.

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.

However, the judges were torn over whether the AFP ought to destroy material seized during the search.

Two justices found the police should destroy the data, but the majority disagreed.

The AFP sought legal advice on what to do with the evidence after the decision was handed down.

In October last year, incoming AFP Commissioner Reece Kershaw flagged an external review of his agency's policies and guidelines around sensitive investigations.

He said police independence and freedom of the press were fundamental pillars of Australian democracy.

Deputy Commissioner McCartney wouldn't say when two ABC journalists who are also the subject of investigations would know if they would face charges. On Tuesday journalist Sam Clark tweeted "622 days" - the time they have been waiting with the prospect hanging over their heads.

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The attorney-general could not say when a separate AFP investigation involving two ABC reporters would be finalised.

"These are not decisions made by ministers," Mr Porter said.

"They're made by the agencies and departments - in this case, the AFP - who has full independent discretionary authority to determine whether to commence, conduct or conclude an investigation.

"If there's questions to be asked about timing, they need to be asked to the AFP."