Elon Musk has accused the UK government of wanting to suppress free speech after ministers threatened fines and a possible ban for his social media site X after its AI tool, Grok, was used to make sexual images of women and children without their consent.

The billionaire claimed Grok was the most downloaded app on the UK App Store on Friday night after ministers threatened to take action unless the function to create sexually harassing images was removed.

Responding to threats of a ban from the government, Musk wrote: “They just want to suppress free speech”.

Thousands of women have faced abuse from users of the AI tool which was first used to digitally strip fully clothed photographs into images showing them wearing micro bikinis, and then used for extreme image manipulation.

Pictures of teenage girls and children were altered to show them wearing swimwear, leading experts to say some of the content could be categorised as child sexual abuse material.

Some users began to demand to see bruising on the bodies of the women, and for blood to be added to the images. Women were shown tied up, gagged and shot.

The technology secretary, Liz Kendall, said on Friday that ministers were looking seriously at the possibility of access to X being barred in the UK.

She said she expected Ofcom, which said this week that it was seeking urgent answers from the platform, to announce action within “days not weeks”.

“X needs to get a grip and get this material down,” she said. “And I would remind them that in the Online Safety Act, there are backstop powers to block access to services if they refuse to comply with the law for people in the UK. And if Ofcom decides to use those powers, they would have the full backing of the government.”

The UK government’s concerns were echoed by the Australian prime minister, Anthony Albanese. Speaking in Canberra on Saturday, Albanese said that “global citizens deserve better”. Australia recently banned the use of social media for under-16s.

“The use of generative artificial intelligence to exploit or sexualise people without their consent is abhorrent,” he said.

“The fact that this tool was used so that people were using its image creation function through Grok is just completely abhorrent. It, once again, is an example of social media not showing social responsibility.”

Some rightwing political figures have tried to frame this as a free speech issue. Responding to the news X faced a potential ban, the former prime minister Liz Truss said: “Starmer is really losing it now.”

X partially restricted access to Grok on Friday. Its public account lost the ability to generate images at the request of free users, leaving the function available only to paid subscribers. It also appeared to have stopped creating bikini images.

The Grok app, however, which does not generate images publicly, is still able to create sexually explicit material from women’s pictures.

Other nudificiation apps are still available. The Labour MP Jess Asato, who campaigns against the sexual abuse and harassment of women, said legislation to ban such apps was urgently needed.

She posted on social media: “It’s not just XAi. This nudification tool was advertised yesterday on @YouTube.

“No rules had been broken @Google said on reporting.

“Our nudification legislation needs to be expedited.”

Google was approached for comment.