UK Prime Minister Boris Johnson is poised to begin phasing out the use of Huawei technology in Britain's 5G network as soon as this year, in a major about-turn, The Telegraph can disclose.
Government Communications Headquarters (GCHQ) is understood to have revised its previous assurance that the risks posed by the Chinese technology giant can be safely managed.
A report due to be presented to the Prime Minister this week is expected to conclude that new US sanctions on Huawei will force the company to use untrusted technology that could make the risk impossible to control.
The report, by GCHQ's National Cyber Security Centre, has concluded that the sanctions, which will bar Huawei from using technology relying on American intellectual property, has had a "severe" impact on the firm that significantly changes their calculations.
Officials are now drawing up proposals to stop installing new Huawei equipment in the 5G network in as little as six months, and to speed up the removal of technology that is already in place. Whitehall figures are now also examining the "ramifications" for existing Huawei equipment in other infrastructure outside 5G.
Such a package of measures would represent a dramatic reversal by the Prime Minister after his decision in January to allow Huawei to build parts of the network.
The report comes as Johnson faces his biggest backbench uprising yet, with Tory MPs threatening a parliamentary "insurgency" if the Government fails to take a tougher approach on Huawei and China.
Debate on the National Security and Investment Bill, which Tories had been preparing to amend to force Johnson's hand on Huawei, is now believed to have been postponed until after the summer, amid fears of a major rebellion. Sir Iain Duncan Smith, who plays a leading role in the 59-strong Huawei Interest Group of Conservatives, said: "Unless the Government now really takes a firm lead they will find that Parliament leads dramatically."
Whitehall sources said the NCSC's report was expected to mark a "fundamental shift" from its previous assurances that led to Johnson allowing Huawei a market share in the 5G network of up to 35 per cent. Its assessment of the potential risks to the UK is now believed to be far closer to that of security agencies in the US.
Trump's administration has classified Huawei as a national security threat amid claims the company has "close ties to the Chinese government and military apparatus". Huawei has said the decision was based on "innuendo and mistaken assumptions".
Oliver Dowden, the Culture Secretary, is expected to provide Johnson with formal advice, including the NCSC's fresh assessment, as soon as this week.
The Prime Minister is likely to then call a meeting of the National Security Council to finalise a new strategy before announcing the measures in Parliament later this month.
A Huawei spokesman said: "Huawei is the most scrutinised vendor in the world and we firmly believe our unrivalled transparency in the UK means we can continue to be trusted to play a part in Britain's gigabit upgrade. It's important to focus on facts and not to speculate at this time."