An unrepentant Malcolm Turnbull has made his third anti-Donald Trump foray in 24-hours to press his argument about the US President’s character, as Australia tries to clinch an exemption from trade tariffs.

The former Liberal prime minister isn’t backing down, insisting Australians shouldn’t be scared of offending Trump’s “huge ego”, despite suggestions his criticism could jeopardise negotiations.

“Surely we should be free to speak the truth,” Turnbull told ABC radio on Tuesday.

“Or are we going to muzzle ourselves for fear of offending Mr Trump?

“What every nation needs to do is to stand up to him, because otherwise it’s a slippery slope.”

Trump criticised Turnbull, who negotiated an exemption during the President’s first term, with America’s 25 per cent tariffs on steel and aluminium imports due to take effect on Wednesday.

The spray happened on the social media platform Truth Social, which is owned by Trump Media, on Monday afternoon (AEDT). It followed Turnbull giving a critical interview to the Bloomberg news service, branding Trump as rude, erratic and playing into China’s hands.

“Malcolm Turnbull, the former Prime Minister of Australia who was always leading that wonderful country from ‘behind’, never understood what was going on in China, nor did he have the capacity to do so,” Trump wrote.

“I always thought he was a weak and ineffective leader and, obviously, Australian’s (sic) agreed with me!!!”

Turnbull lost the prime ministership in a Liberal leadership spill and was not voted out by the public.

He returned fire on Monday night, telling ABC TV that Australia had to be realistic about Trump’s impact and warning China would take advantage of his “erratic” behaviour.

On ABC radio on Tuesday morning, he re-iterated and added to his comments.

“He’s a bully, he seeks to achieve dominance and he gets dominance by intimidating people,” Turnbull said.

“I talk about these issues and write about them all the time, so I’ve got no idea why Donald Trump suddenly decided to respond on the way he did.

“You’d think he’d have better things to do late at night than writing abusive posts about Australian former politicians.”

Asked by Radio National host Sally Sara about the timing of his comments, Turnbull took aim at the ABC.

“I’m a little bit concerned by the way you raise this, too, because [7.30 host] Sarah Ferguson did the same thing last night,” he said.

“It troubles me … both of you are distinguished journalists on the ABC. Are you suggesting that we should engage in self-censorship in Australia for fear of offending the huge ego of Donald Trump?”

Turnbull said “every week is a good week to tell the truth”.

“You know, the markets are being roiled, the world is being roiled,” he said.

“Trump has essentially switched sides and is now favouring [Russian leader Vladimir] Putin in the Ukraine conflict, right around the world. I mean, maybe you should send a memo to Mark Carney, the new Prime Minister of Canada, and ask him whether he shouldn’t have criticised Donald Trump for trying to bankrupt his own country.”

Turnbull has previously said Trump is unpredictable and could not be trusted to take military action if Australia, long touted as a trusted and important US ally, was attacked.

With the US tariffs due to come into effect on Wednesday, it is still unclear whether Australia will be exempt.

Australia has argued it should be because it imports more from the US than it exports – the same argument Turnbull used successfully when he was PM during Trump’s first term.

But Turnbull said the chances of another exemption were “very, very low” as the administration regretted its previous exclusions.

“I think this time there will be no exemptions, and they will apply right across the board,” he said.

The federal government has downplayed Turnbull’s comments.

“Malcolm Turnbull is not a member of the government,” minister Amanda Rishworth told the Today show.

“Our government is absolutely focused on making sure that we are standing up for Australian exporters.”

Opposition Leader Peter Dutton said while he didn’t agree with the Trump’s analysis of Turnbull’s term, the focus should remain on Prime Minister Anthony Albanese.

“The most important aspect now is not the tit-for-tat,” he told Seven’s Sunrise program on Tuesday.

“The Prime Minister needs to, frankly, roll his sleeves up and get this deal done so that workers jobs and the economic activity can be preserved.”

-with AAP