Image caption Mel Greig and Michael Christian's prank call drew widespread coverage

The Australian radio station that made a prank call to the Duchess of Cambridge's hospital "broke the law", the country's media watchdog has said.

The finding came in a confidential, preliminary report by the Australian Communications and Media Authority (ACMA), which emerged in a court case.

It said 2Day FM acted illegally by airing the phone call without consent.

Lawyers for 2Day FM's owner, Southern Cross Austereo, are seeking to block the report, according to local media.

The document came to light as part of their Federal Court hearing, in which they argue the ACMA does not have the power to make a criminal finding, only the courts do.

Australian Federal Police are currently investigating the call.

Nurse Jacintha Saldanha was found dead in December, three days after DJs Mel Greig and Michael Christian duped her into transferring a call to the Duchess of Cambridge's hospital ward.

A ward nurse at King Edward VII's Hospital then gave the DJs details about the condition of the Duchess, who was being treated for severe morning sickness at the time.

Christian returned to work two months after the prank call, while Greig remains off air and is suing her employer for failing to provide a safe workplace.

She is due to give evidence in person at the London inquest into Saldanha's death. The inquest was delayed in July for the second time to give coroner Dr Fiona Wilcox time to "seek more information".