The claim that the UK is working with Canada and Australia to launch a coordinated ban on X is mostly true because multiple independent sources, including official government-related social media accounts and news outlets, report ongoing discussions and considerations of a joint ban, although no formal ban has yet been enacted.
The UK is working with Canada and Australia to launch a coordinated ban on X, per the Telegraph

X could be banned in UK amid sexualised AI images concerns - The Independent
Source: independent.co.uk
Key Evidence
Multiple sources including official government-related social media accounts and reputable news outlets report that the UK, Canada, and Australia are discussing a coordinated ban on X due to concerns over AI-generated indecent images and regulatory compliance.
The Telegraph is cited as a source for this information.
However, no formal ban has been confirmed yet.
What the Evidence Shows
Several sources indicate that the UK government, alongside Canada and Australia, is actively discussing or considering a coordinated ban on X, the social media platform formerly known as Twitter. This is primarily in response to concerns over indecent AI-generated images and regulatory compliance under the UK's Online Safety Act.
Official and semi-official social media posts explicitly mention government cooperation between these countries to send a "powerful message" to Elon Musk by potentially banning X together.x.comx.comPolitics UK on X: "🚨 NEW: The Government is working with Canada and Australia...
x.comx.comRemarks on X: "JUST IN: UK, Canada and Australia discuss coordinated plan to ban...
News outlets such as The Independent, The Guardian, and The Telegraph report on the UK government's threat of sanctions or bans on X due to safety concerns related to AI content moderation failures.independent.co.ukindependent.co.ukX could be banned in UK amid sexualised AI images concerns
telegraph.co.uktelegraph.co.ukUK threatened with sanctions if Starmer bans X+2 more
Additional reports from Bitget News and Ainvest confirm that Canada and Australia are part of these discussions, indicating a trilateral approach rather than unilateral action by the UK.bitget.combitget.comThe UK, Canada, and Australia consider jointly banning Musk's X
ainvest.comainvest.comUK, Canada and Australia consider coordinated plan to ban Elon Musk's X
However, none of the sources confirm that a formal ban has been implemented yet; rather, these are ongoing considerations or plans. Some sources also highlight that any ban would be an extreme measure under the Online Safety Act requiring court agreement.
Therefore, while the claim about working together on a coordinated ban is supported by multiple credible reports, it remains at the discussion or planning stage rather than an executed policy.