Two journalists were asked for their fingerprints just months before police raided the ABC's headquarters in Sydney over leaked information.
Federal police wanted to fingerprint two ABC journalists involved in a series of stories about Australia's special forces allegedly carrying out unlawful killings in Afghanistan.
A letter from the Australian Federal Police to journalists Dan Oakes and Sam Clark was emailed on 1 April - two months before AFP officers raided the ABC's Sydney headquarters seeking leaked documents relating to the stories.
The ABC said the email stated the AFP was "requesting your consent to a forensic procedure being the copying of your finger and palm prints", with the two journalists being suspects in relation to three alleged offences.
The ABC declined to comment further on Monday, beyond confirming the AFP request had been received.
The revelation followed a report in the Sydney Morning Herald which said the AFP had sought Mr Oakes' travel details from Qantas.
Labor's home affairs spokeswoman Kristina Keneally blamed the coalition for not doing enough to protect press freedom.
"If journalism is not a crime in Australia, why is the Morrison government treating journalists like criminal suspects?" she said in a statement.
The ABC's managing director David Anderson has asked for the investigation to be dropped and is pursuing legal action to declare the search warrant involved in the raid invalid.
Home Affairs Minister Peter Dutton last week rejected calls for the police action to be dropped, saying having leaked top-secret documents was an offence.
He said nobody was above the law but insisted he would not interfere in the investigation.
The ABC is also seeking a permanent injunction stopping the AFP accessing the electronic files removed from Ultimo on a sealed USB stick.
Former military lawyer David McBride has been committed to stand trial charged with theft of Commonwealth property, three counts of breaching the Defence Act and unauthorised disclosure of information.
The Australian Federal Police Association in June backed the professionalism and integrity of the officers involved in executing the search warrant.
News Corp journalist Annika Smethurst is also under police investigation after publishing a separate story based on leaked government information, which led to a raid on her Canberra home.
The parliamentary joint committee on intelligence and security has begun an inquiry into the impact of the exercise of law enforcement and intelligence powers on the freedom of the press.
Submissions to the inquiry close on 26 July and it is due to report in October.