Royal prank call investigation blocked: watchdog

Radio DJs Michael Christian, left, and Mel Greig appear during an interview on Australia's Channel Nine over the infamous and ultimately tragic royal prank phone call. Photo / AP

Radio station 2Day FM is attempting to block an investigation into its infamous royal prank telephone call.

The Sydney broadcaster has filed a NSW Federal Court application arguing that Australia's media watchdog has no power to continue a key part of its ongoing probe into the December 2012 incident.

British nurse Jacintha Saldanha, 46, took her own life three days after 2Day FM's Mel Greig and Michael Christian duped her into passing them on to a ward nurse who gave out details about the Duchess of Cambridge's stay at London's King Edward VII hospital.

The prank call was recorded and broadcast.

The Australian Media and Communications Authority (ACMA) is investigating whether 2Day FM breached its licence conditions by illegally using a surveillance device to record the call.

The radio station argues that the ACMA has no power to decide whether use of the surveillance device constitutes an offence, pointing out that police have not investigated the case.

2Day FM is seeking a Federal Court ruling, with hearings due to begin in Sydney on July 17, preventing the ACMA from finding that it breached its licence.

"The ACMA has no power to investigate whether the recording of a telephone call breaches state or federal laws,'' 2Day FM's parent company Austereo said in a statement.

"The agencies which do have that power have not conducted an investigation or sought any information from Today FM.

"Today FM also considers that the recording of the prank call did not breach any law.''

Neither party would comment on speculation that a preliminary ACMA report has already concluded that 2Day FM may be stripped of its broadcast licence.

The report has been handed to 2Day FM but neither party was willing to discuss its contents when contacted by AAP.

The ACMA released a statement confirming it would contest 2Day FM's court application.

- AAP