Sensitive discussions between Foreign Minister Julie Bishop and Prime Minister Tony Abbott were conducted over secure phone lines and were not monitored, the prime minister says.
That follows a media report that Ms Bishop's mobile phone was compromised while she was overseas.
The Herald Sun said Australian intelligence officials seized the phone when she returned from a trip negotiating access to the MH17 crash site in the Ukraine.
Malaysia Airlines flight MH17 was downed in eastern Ukraine last month, killing 298 passengers and crew.
Australian intelligence agencies know which country those responsible for compromising the phone were from, the Herald Sun report said.
The phone was not used to discuss sensitive communications and was replaced.
Mr Abbott said he hadn't discussed this with Ms Bishop.
"It's well known that some countries do seek to, I suppose, target the phones of significant members of the Australian government. It's the sort of thing that does happen from time to time," he told reporters in Lithgow, NSW.
But I can assure the Australian people that the very significant discussions that Julie Bishop was part of with me and with other members of the National Security Committee in recent times were all done over secure lines."
Opposition finance spokesman Tony Burke said he was aware of a report of this incident.
"From the reports that we have seen the intelligence agencies have taken it seriously and are dealing with it," he told reporters in Sydney.