The Prime Minister's cyber security advisor says the use of smartphone communication apps such as WhatsApp have not been approved by the Australian Signals Directorate (ASD) for transmitting sensitive information.

Key points: Cyber security adviser says smartphone apps not approved for sensitive communications

Cyber security adviser says smartphone apps not approved for sensitive communications Brandis uses WhatsApp to communicate with PM and other cabinet members

Brandis uses WhatsApp to communicate with PM and other cabinet members Brandis declines request to table Cabinet's WhatsApp chats to estimates committee

Attorney-General George Brandis has revealed he uses the app to communicate with other Cabinet ministers, including Prime Minister Malcolm Turnbull.

Alastair MacGibbon has told a Senate estimates committee apps such as WhatsApp "can increase privacy and security" based on their encryption, compared to conventional SMS messages, emails or phone calls.

But he said that, to his knowledge, the ASD had not approved the use of any such smartphone aps for classified or sensitive communications.

"In the information security manual published by ASD, it tells you the structure and nature of communication systems and anything that's classified needs to go over those systems," he said.

Senator Brandis confirmed he used WhatsAapp to communicate and said the conversations conducted on the app were "entirely unremarkable", but refused to table the communications to the estimates committee.

"I can assure you, having myself communicated with the Prime Minister and other Cabinet colleagues on WhatsApp, there has never been an occasion, ever, which the material on WhatsApp has been other than that of an extremely routine nature," he said.

"Never, ever, ever has there been an occasion when a sensitive or national security matter has been reduced to that form, for obvious reasons."

Alastair MacGibbon says the ASD has not approved Whatsapp for classified or sensitive communications. ( Reuters: Nacho Doce )

Mr MacGibbon confirmed he had also used WhatsApp to communicate with Mr Turnbull but was adamant it was "nothing at all of a national security nature".

Senator Brandis declined to say whether there was a group chat with Cabinet groups, arguing it was a "definitional" issue, but that any communications using the app was "entirely unremarkable".

He declined a request from Senator Wong to table the chat to the estimates committee.

The Government's information watchdog said the information could also be handed over as part of any Freedom of Information requests.

WhatsApp, which is owned by social media giant Facebook, says it has a number of servers located around the world.