The second-time presidential hopeful roasted Australia's Washington-based US ambassador in an interview on London's GB News network on Wednesday, calling him "a little bit nasty" and warning that he would "not be there for long".

The comments have sparked a political firestorm in Australia, as opposition politicians warn that if Mr Trump returns to the presidency in November his hostile stance could harm diplomatic relations.

But ex-Liberal minister and Australia's former high commissioner to the UK George Brandis said Mr Trump's comments don't amount to much, noting Mr Trump barely seemed to know who Dr Rudd was.

"Donald Trump is infamous for making rather wild and off-the-cuff claims that don't amount to very much," he told ABC radio on Thursday.

"It's obviously something that the government should keep an eye on, but I wouldn't over-interpret it."

Nigel Farage, a British conservative political operative and the man who interviewed Mr Trump, has claimed Australia will have no alternative but to "pull Kevin Rudd out".

For Australia's trilateral security alliance with the US and UK to flourish, the Commonwealth needed an ambassador who could talk to the president, Mr Farage said.

While Mr Trump had a history of working with high profile figures after publicly bullying them, this was unlikely to apply to Dr Rudd, he claimed.

"There's more chance of him having tea with Kim Jong Un," Mr Farage told Nine's Today program.

"That relationship clearly is not going to work.

"A Trump victory (means) maybe Mr Rudd's home for Christmas."

But Mr Brandis challenged Mr Farage's comments.

"Nigel Farage is a charming charlatan who's building a reputation as a broadcaster in the United States," he said.

"He is interested in attributing as much importance to his interviews as possible, but I don't think Nigel Farage's views on this matter."

Australia's senior diplomatic representatives should have bipartisan support or their authority and influence diminishes, Mr Brandis said, after opposition MPs including Barnaby Joyce and David Littleproud cast doubt on Dr Rudd's ability to do his job in a new Trump regime.

"That's plainly not in Australia's national interest," Mr Brandis added.

Meanwhile, the federal government, including minister Mark Butler, support Dr Rudd.

"We're very confident that whatever happens in November, he'll be able to work with all US administrations," he told Nine's Today show.

"Kevin Rudd is very widely respected right across the aisle."

Before Dr Rudd was appointed Australia's US ambassador, he decried Mr Trump as a "traitor to the west" and "the most destructive president in history" who "drags America and democracy through the mud".

Dr Rudd is not the only Australian political figure to criticise the Republican nominee.

Former Liberal defence industry minister Christopher Pyne in 2020 wrote Mr Trump "does not have the emotional equipment to be president" while ex-treasurer Josh Frydenberg in 2015 called him a "dropkick".

Mr Brandis has admitted he is also "not a fan" of Mr Trump citing his isolationist tendencies, lukewarm support for NATO, warmth towards Russian leader and "one of the most evil men in the world" Vladimir Putin, and his failure to speak out about the invasion of Ukraine.

Australian Associated Press