Elon Musk has called the Australian government “fascists” over new legislation aimed at tackling deliberate lies spread on social media.

Social media companies could be fined up to 5% of their annual turnover under the commonwealth’s proposed laws.

Musk, the US billionaire who owns the social media platform X, formerly Twitter, responded to a post about Australia’s measures with one word.

“Fascists,” he wrote.

But the federal minister Bill Shorten said Musk was inconsistent on free speech.

“When it’s in his commercial interests, he is the champion of free speech; when he doesn’t like it, he’s going to shut it all down,” he said on Channel Nine’s breakfast show on Friday.

The assistant treasurer, Stephen Jones, said Musk’s comment was “crackpot stuff”. Jones told ABC TV that the government’s new bill on misinformation and disinformation was a matter of “sovereignty”.

“Whether it’s the Australian government or any other government around the world, we assert our right to pass laws which will keep Australians safe – safe from scammers, safe from criminals,” he said.

“For the life of me, I can’t see how Elon Musk or anyone else, in the name of free speech, thinks it is OK to have social media platforms publishing scam content, which is robbing Australians of billions of dollars every year. Publishing deepfake material, publishing child pornography. Livestreaming murder scenes. I mean, is this what he thinks free speech is all about?”

The federal aged care minister, Anika Wells, told ABC radio she had “yet to meet [a fascist] in the government”.

Australia’s misinformation legislation would give the communications watchdog powers to monitor and regulate content on digital platforms.

It would also allow it to approve an enforceable industry code of conduct or introduce standards for social media companies if self-regulation was deemed to fail.

This is not the first time Musk has battled Australian authorities.

In April the eSafety commissioner issued an edict to X to remove graphic content after clips of the Sydney bishop Mar Mari Emmanuel being stabbed remained on the platform.

During the months-long saga, Musk accused the government of suppressing free speech.

Several politicians hit back, with the prime minister, Anthony Albanese, labelling him an “arrogant billionaire”.

In June the eSafety commissioner discontinued the federal court proceedings. A separate administrative appeals tribunal review of the notice issued to X is expected to be heard in October.

The eSafety commissioner, Julie Inman Grant, told the ABC last month that X had seven ongoing legal matters with her office related to notices issued by the commissioner.

In the federal court this week X challenged a $610,500 fine issued last year, arguing the original notice was issued to what was then Twitter Inc, a company that ceased to exist in March 2023, and the legislation did not account for the merger. The court reserved its decision.

Separately, millions of users of X in Brazil were cut off from the platform this month after a dispute between the rightwing tech billionaire and Brazil’s top court over X refusing to purge anti-democratic and far-right voices from the site in the wake of the January 2023 uprising in the capital, Brasília, carried out by supporters of the former far-right president Jair Bolsonaro.