"I have the greatest confidence that ASIO officers work with integrity and do not leak information to third parties,as has been repeatedly implied in the media,"he told senators at a hearing following the leak.

Opposition Leader Anthony Albanese at the time accused the government of providing the material toThe Australian.

"This government is undermining our national security with some of their rhetoric and it is undermining our national security by leaking classified documents in a strategic way designed to put spin on it and designed to scare people,"he said.

A revisedmedical transfer bill passed Parliament against the wishes of the government and Prime Minister Scott Morrison has vowed to repeal it later this year.

Labor's Home Affairs spokeswoman Kristina Keneally said the decision to not investigate the leak was an"absolutely breathtaking development".

"In light of this week's media raids,many Australian citizens and media outlets will have questions about why some leaks of classified information lead to raids and other leaks do not,"Senator Keneally said.

"The leak of classified advice,smack in the middle of a parliamentary debate about the medevac bill,clearly had political implications and[Home Affairs Minister] Peter Dutton must explain where this leak came from."

An AFP spokesperson said the referral was assessed in accordance with standard AFP protocols.

"Due to the limited prospects of identifying a suspect,it was not accepted for investigation. The AFP considers this matter finalised."

The organisation is facing scrutiny over twin raids on the home of News Corp journalist Annika Smethurst and the headquarters of the ABC over separate stories published in 2017 and 2018.

Smethurst's report revealed top bureaucrats had discussed giving Australia's cyber spies broader powers. The ABC's stories used leaked Defence information to accuseAustralia's elite special forces in Afghanistan of killing unarmed men and children.

Police are considering whether the journalists and media organisations subject to the search warrants may have committed a crime by publishing the sensitive information.

AFP acting commissioner Neil Gaughan rejected claims police were"trying to intimidate journalists or conduct a campaign against the media"and argued his officers were enforcing the laws set by Parliament.

Asked on Friday whether the source of classified leaks can sometimes be inside the ministerial wing at Parliament House,Mr Morrison replied,"no one is above the law"but said he would not second-guess police investigations.