'Nuts': Kevin Rudd's scathing attack on US President Donald Trump

Former prime minister Kevin Rudd has launched a scathing attack on Donald Trump, declaring the American president to be "nuts" and warning that China could step into a potential regional power vacuum.

"I think the general consensus amongst anyone concerned with a public policy process, domestic or international, thinks he's nuts," Mr Rudd said on the ABC's Q&A on Monday night, in response to a question about US voter support for the President.

Mr Rudd, now based in the US but in Australia promoting his memoir, said he had remained silent for the first six months of the Trump presidency.

But, he said: "One small example … I spent a huge amount of time as PM getting America to be accepted as a member of something called the East Asian Summit. The whole idea was to get the Americans into regional diplomatic institutions concerned about long-term regional security. Prior to that they were outside.

Kevin Rudd was scathing about Donald Trump.Credit: Andrew Meares

"That was two years of work. Wasn't easy. Finally persuaded the Obama Administration to do it and the rest of the region to say 'OK, we'll cop it'. One meeting a year. The only multilateral forum that says, 'Get together and we'll talk about regional security', from North Korea down. Eighteen heads of state around the table.

"And basically what I've just seen out of Washington is this guy [Trump] has decided not to go … people worry about the future role of China in the region. If that is their concern, for God's sake, this is just an open door for China to be in that conference and to dominate it."

Mr Rudd said there was still strong support for Mr Trump among Republican Party voters.

"Now that is the scary thing. For the future, we need action by both the [US] Senate and the house leadership to rein him in. But they are terrified by the continued support this guy has out there and anywhere from Alabama to the mid-west."

Former prime minister Kevin Rudd is not a fan of US President Donald Trump.Credit: AP

Asked if Australia should reconsider the ANZUS alliance given his reservations about Mr Trump, Mr Rudd said: "The President of the US does not equal the US. We will see what happens in three years time. You don't make a single decision on, shall I say, the unique qualities of the current occupant of the White House."

Mr Rudd also repeated his attacks on Wayne Swan, the treasurer in his government, and was asked who he should have chosen for the position instead.

"Lindsay Tanner," he replied. "I had many sleepless nights on what to do. I wanted Lindsay in that area, in the economic domain. He would have been a brilliant treasurer."