Image editing on X's Grok AI tool has been limited to paid subscribers, according to a message displayed by the chatbot - with the changes described as "insulting" by Downing Street.

Users were able to upload a picture and ask Grok to alter the image, but the AI system now replies to requests with this message: "Image generation and editing are currently limited to paying subscribers."

It comes after the Internet Watch Foundation (IWF) warned criminals used Grok to create child sexual abuse imagery.

On Friday, Downing Street said changes to limit the use of chatbot Grok's image editing tool to paying users are "not a solution" but prove the social media platform can move quickly when it wants to.

The prime minister's spokesman said the move "simply turns an AI feature that allows the creation of unlawful images into a premium service".

"It's not a solution. In fact, it's insulting the victims of misogyny and sexual violence," he said.

Prime Minister Sir Keir Starmer previously said Grok being used to create illegal images was "disgraceful" and "disgusting". He told X to "get their act together" and "get a grip on this".

"If another media company had billboards in town centres showing unlawful images, it would act immediately to take them down or face public backlash," his spokesman added.

X and xAI, both owned by billionaire tycoon Elon Musk, have come under fire in recent days after numerous users, mainly women, posted saying they had seen AI-generated sexual images of themselves on X.

Ngaire Alexander, head of hotline at the IWF, said on Thursday: "Following reports that the AI chatbot Grok has generated sexual imagery of children, we can confirm our analysts have discovered criminal imagery of children aged between 11 and 13 which appears to have been created using the tool."

Regulator Ofcom said it made "urgent contact" with X following these reports, with the prime minister's spokesman saying that "all options" are on the table, including for Ofcom to use its powers to "take any action".

'Not good enough'

Grok's move to limit the editing of pictures to paid subscribers was "not good enough", Hannah Swirsky, head of policy at the IWF, said.

"This move does not undo the harm which has been done. We do not believe it is good enough to simply limit access to a tool which should never have had the capacity to create the kind of imagery we have seen in recent days."

She said companies should create products that are "safe by design" and urged government and regulators to "force them" to design safer tools.

"Sitting and waiting for unsafe products to be abused before taking action is unacceptable," she added.

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On Wednesday, Musk said a new version of Grok had been released and urged users to update their app, although it was not immediately clear what updates the new version contained.

X insisted on its X Safety account that "anyone using Grok to make illegal content will suffer the same consequences as if they uploaded illegal content".

The company said it takes action against illegal content, including child sexual abuse material, "by removing it, permanently suspending accounts, and working with local governments and law enforcement as necessary".