Officials from the prime minister's department appear to have no written records of a controversial phone call US President Donald Trump made to Scott Morrison.
The prime minister agreed to help Mr Trump with a contentious inquiry into the FBI during a phone conversation on September 5.
No one from the department sat in on the call and they were not aware of any of the prime minister's parliamentary staff doing so either.
"I received a brief readout from the office after the call had taken place ... It was a verbal readout," senior official Justin Hayhurst told a Senate committee hearing on Monday.
Asked whether he wrote it down, he replied: "Me? I didn't take notes of that readout, no."
"I alerted (deputy secretary Caroline) Millar, who was away at the time, that the call had taken place and I would tell her about it when she returned to Canberra."
The question of who from the prime minister's office had briefed him was taken on notice.
Mr Morrison has said Mr Trump was simply seeking a point of contact within the Australian government for the investigation.
But officials who were asked repeatedly who the prime minister had nominated could not reply and also took that on notice to answer later.
The inquiry is widely seen as a partisan attempt by the Trump administration to discredit an earlier investigation into Russian interference in the 2016 US election.
The initial probe was sparked by a tip-off from former Australian diplomat Alexander Downer.
Australian Associated Press