Changes to Elon Musk's artificial intelligence (AI) chatbot Grok only serve to make creating deepfakes a "premium service" and are "insulting" to victims of misogyny and sexual violence, Downing Street has said.
The Prime Minister's spokesman said changes to limit usage of chatbot Grok's image editing tool to paying users are "not a solution" but do prove that social Elon Musk's social media site X can move quickly when it wants to.
The move comes after regulator Ofcom said it made "urgent contact" with X, which created the integrated AI chatbot, following reports users have prompted the tool to generate sexualised images of people, including children.
Grok is now telling people making such requests that only paid subscribers are able to do so - meaning their name and payment information must be on file.
The Prime Minister's spokesman said: "That move... that 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.
"What it does prove is that X can move swiftly when it wants to do so"
"You heard the Prime Minister yesterday. He was abundantly clear that X needs to act and needs to act now, it is time for X to grip this issue."
"If another media company had billboards in town centres showing unlawful images, it would act immediately to take them down or face public backlash."
He reiterated that "all options" are on the table including for Ofcom to use its powers to "take any action".
Asked about a US congresswoman's threat to bring legislation to sanction Sir Keir and "Britain as a whole" if the UK bans X, the No 10 spokesman said the Government is focusing on stopping the creation of unlawful images on the site.
Representative Anna Paulina Luna, of Florida, said Sir Keir Starmer should "reconsider this course of action, or there will be consequences".
The spokesman would not be drawn on whether the Government might heed calls to boycott X and said the focus at this time is "stopping these abhorrent images".
He seemed to suggest that the Government would defer to Ofcom on what action to take.
Sir Keir and Technology Secretary Liz Kendall have backed the regulator to take any enforcement action deemed necessary.
Shadow business secretary Andrew Griffith rejected the idea of boycotting or banning X.
He told the Press Association: "You've got to be where the debate is taking place, and that's all social media.
"Look, let's just be really clear: it's not X itself or Grok that is creating those images, it's individuals, and they should be held accountable if they're doing something that infringes the law."
Meanwhile, an internet safety organisation said its analysts have confirmed the existence of "criminal imagery of children aged between 11 and 13 which appears to have been created using the (Grok) tool".
Grok's move to limit the tool to paying users is "not good enough", The Internet Watch Foundation (IWF) said.
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.
"Companies must make sure the products they build and make available to the global public are safe by design.
"If that means governments and regulators need to force them to design safer tools, then that is what must happen. Sitting and waiting for unsafe products to be abused before taking action is unacceptable."
Mr Musk has previously insisted "anyone using Grok to make illegal content will suffer the same consequences as if they uploaded illegal content".
X has 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".