Former leader of the free world Donald Trump has lashed out at former Australian PM Kevin Rudd, characterising him as “not the brightest bulb”.

In an interview with former far-right British politician Nigel Farage on London’s GB News channel, the rebooted US presidential hopeful responded to Rudd’s previous criticism of him.

Prior to his appointment as US ambassador, Australia’s 26th prime minister was a vocal critic of the Republican president, calling Trump a “traitor to the west” and “the most destructive president in history” who “drags America and democracy through the mud”.

In his sit-down with Trump on Tuesday (US time), Farage said “our friends at Sky News Australia wanted me to ask you” about Australia’s relationship with the US, particularly after the appointment of Rudd as ambassador (Farage described Rudd as a “former Labor MP”).

“He has said the most horrible things … And he’s now Australia’s ambassador in Washington. Would you take a phone call from him?” he said.

Trump responded with a warning to Rudd.

“I don’t know much about him, I heard he was a little bit nasty,” he said.

“I hear he’s not the brightest bulb … if he’s at all hostile, he will not be there long.”

The US presidential election in November is expected to be a rematch between Trump and Democrat President Joe Biden. Biden’s approval rating has continued to slip, while the former president contends with multiple criminal charges.

On Wednesday, Deputy Opposition Leader Sussan Ley said politicians should wait for the outcome of the US election and avoid commenting on other countries’ domestic political situations.

“I’m not going to make commentary on what might transpire … I think people in this government now might be wondering why they made the comments they did at the time,” she told Sky News.

“Kevin Rudd is our ambassador, we do want him to succeed because he represents the national interest.”

Nationals leader David Littleproud was more critical.

“I find it extraordinary that Kevin Rudd, who’s had experience in the diplomatic corps and then as a prime minister, has wanted to weigh in on foreign politics and then ended up as the ambassador in the United States,” he told Sky News.

“It shows that he was a poor choice to start with. And now if we have a Trump administration, that we’re going to have a very difficult time in negotiating with the new administration, particularly with things as important as AUKUS.”

But Foreign Minister Penny Wong defended her former colleague, noting his adeptness at engaging with both Democratic and Republican members of US Congress.

“Mr Rudd is a very effective ambassador,” she said.

“I’d point you in particular to the phenomenal amount of work which has been done on AUKUS in the period that he’s been ambassador.

“His experience and skills mean he will be able to work closely with whomever is elected by the American people.”

-with AAP