Fears for Britain's safety are mounting after it emerged a US AI company had blocked the UK from testing its latest model.Under orders from Donald Trump, AI giant Anthropic failed to submit its latest model to Britain's AI Security Institute, which tests the intelligence before it is unleashed on the public.Terrifyingly, this came as a top Anthropic researcher on Wednesday accused AI companies of 'gambling with people's lives' in relentlessly developing superintelligent technology.An Anthropic science lead then admitted that AI had more than a 10 per cent chance of killing 'all humans' within the next decade.President Trump in June ordered Anthropic to block foreign nationals from using its cyber security-focused models Fable and Mythos over national security concerns.In response, Anthropic said it would 'abruptly disable' its most advanced models for all foreigners. Anthropic safety researcher Jacob Coxon announced on Wednesday he was stepping down from Anthropic after three years over AI companies pursuing a 'hubristic gamble' with the human race Under orders from Donald Trump , AI giant Anthropic failed to submit its latest model to Britain's AI Security Institute, which tests the intelligence before it is unleashed on the publicFormer armed forces minister Al Carns asked on Wednesday: 'What is the biggest security threat? China? Russia? Iran? North Korea? 'None of them. It's a few Silicon Valley companies whose founders will become billionaires by the time these systems hit the market'And on Wednesday it emerged Anthropic had for the first time excluded Britain's AI Security Institute (AISI) from testing its latest model Claude Mythos 5.1 – despite the AISI being a world leader on containing the risks of AI.It follows the Daily Mail revealing in July that all five models the AISI had tested tried to trick their way round the security controls they had put in place, with OpenAI suffering its own leak just days previously.When asked by Lib Dem leader Ed Davey on Wednesday about the revelations, first reported by the Financial Times, the Prime Minister said: 'He is absolutely right that AI poses risks to our national security, but it also could be the source of solutions to keeping us safer.'However, Anthropic's move saw fears over AI reach a fever pitch on Wednesday, with politicians of all stripes voicing concern.In a lengthy social media post, former armed forces minister Al Carns asked: 'What is the biggest security threat? China? Russia? Iran? North Korea?'None of them. It's a few Silicon Valley companies whose founders will become billionaires by the time these systems hit the market.'And Reform UK's Danny Kruger wrote on X: 'If true, this is hugely concerning. The UK is losing access to frontier models right at the point where recursive self-improvement (AIs using AI to make the next AIs even more capable) could be kicking in, and huge advances are being made - with huge risks.'This jeopardises British national security. The government must explore all diplomatic options to retain access to the frontier, including rapidly building secure compute that our allies can verify and trust.'Ben Spencer, shadow minister for AI, added: 'The UK must retain the ability to assess and manage the risks from advanced AI systems.'The UK's world-leading Artificial Intelligence Security Institute (AISI) was established by the previous Conservative Government to assess the risks of AI systems to society, public safety, and national security.'The Government must act now to ensure it has access to all new frontier models to perform this vital role.' Anthropic for the first time excluded Britain's AI Security Institute (AISI) from testing its latest model Claude Mythos 5.1 – despite the AISI being a world leader on containing the risks of AIIt comes as MPs are stepping up measures in Parliament to address the risks posed by AI.Labour MP for Leeds Central and Headingley Alex Sobel on Tuesday brought forward his Artificial Superintelligence Security Bill to the Commons, which would prohibit the development and operation of superintelligent AI.He told the Mail: 'We are seeing more and more incidents of AI models escaping testing environments and acting maliciously alongside more working for Frontier AI companies quitting or giving apocalyptic warnings.'It's why we need both domestic regulation and international agreement before AI is beyond human control'.Business and Trade Committee chair Liam Byrne has also written to AISI director Henry de Zoete accusing the Government body of delaying responding to a request to meet.This comes as Anthropic safety researcher Jacob Coxon announced on Wednesday he was stepping down from Anthropic after three years over AI companies pursuing a 'hubristic gamble' with the human race.In an explosive post online, Coxon wrote that 'the people building AI earnestly believe that it could kill us all by the end of the decade' and that they are 'racing straight to self-improving superintelligence and gambling with our lives'.He added: 'Do not underestimate the power of this technology. These will soon be superhuman systems that can hack anything, revolutionize any field overnight, and acquire real power and resources.'We have all witnessed the progress in each of these domains, and progress is not slowing.'Responding to Mr Coxon, Evan Hubinger, who leads alignment science at Anthropic said: 'Jacob is correct here—we really do earnestly believe AI could kill all humans! I personally think it is >10% within the next decade.'I believe Anthropic is trying its best, but we do not yet have a plan to solve alignment for superintelligence and are not clearly on track.'I think the risk from present models is low. What I am worried about is superintelligence arising from recursive self-improvement, as we have said is happening faster than we thought.'Darren Jones, a Cabinet Office minister under Keir Starmer, called jointly on Andy Burnham and both secretary generals of the United Nations and OECD on Wednesday to introduce a 'new multinational treaty' for safely developing superintelligence.In a letter, Mr Jones wrote: 'We need a new multi-national treaty for the regulated and safe development of superintelligence.'Not a ban on innovation or scientific endeavour but a safety-first approach to the rapid development of this technology.'This comes as British AI experts warned this week the UK risks falling behind the world pack racing to develop AI.Giving evidence in Parliament on Monday, the Alan Turing Institute's George Balston said he has 'a concern about the UK's capability to keep up with AI and how that relates to sovereignty'.He added the UK 'must have some capacity' at the frontier or risk being 'cut off' from key capabilities using AI.A Cabinet Office spokesperson said: 'The UK is a world-leader in AI security and we have the best-funded, best-resourced security institute globally.'The AI Security Institute continues to collaborate closely with industry partners, including Anthropic, to make models safer. Only last week it tested OpenAI's most powerful model GPT-6 Astra before public release.'These risks do not stop at national borders and no country can tackle them alone. The UK will continue to test the most advanced models, build a rigorous scientific understanding of their capabilities and risks, and ensure policy decisions are grounded in the evidence.'