Boris Johnson now has “sound technical reasons” to reverse his decision to allow the Chinese firm Huawei to play a role in building the UK’s 5G infrastructure, a former head of MI6 said on Sunday. Sir John Sawers said new US sanctions imposed on the company meant that allowing Huawei to expand its grip on the UK telecoms market posed security risks that did not apply when the government announced a compromise solution in January giving it up to 35% of the market. Sawers spoke out following reports – not denied by the government – that the National Cyber Security Centre has also concluded that the balance of risk has changed, and that Huawei must be excluded from 5G. The decision, which is expected to be confirmed by the national security council within the next fortnight and announced in a statement to parliament before the summer recess, will be warmly welcomed by many Conservative MPs, 38 of whom rebelled in a vote on this issue in March. In an article for the FT, Sawers said the original decision to allow Huawei a partial role in building 5G was a “reasonable balance” but that was no longer the case because of the sanctions, which would stop the firm using technology reliant on American intellectual property. As a result “reliable non-Chinese suppliers … can no longer work with the company” and “UK intelligence services can therefore no longer provide the needed assurances that Chinese-made equipment is still safe to use in the UK’s telecoms network,” Sawers said. He went on: “There are now sound technical reasons for the UK to change January’s decision … The security assessment is now different because the facts have changed.” Tobias Ellwood, the Conservative chair of the Commons defence committee, told Sky News that it was “very wise” of the government to rethink this issue. He said as well as there being technical reasons for objecting to Huawei having a stake in 5G, China’s handling of the coronavirus outbreak and its security crackdown in Hong Kong showed that there were also political reasons for treating China with more caution. The original decision to allow Huawei to play a role in constructing Britain’s 5G network was taken because western companies could not compete on price or expertise. But the firm was never able to successfully refute suggestions that ultimately it is under the control of the Chinese state, meaning a hostile power could have leverage over critical UK infrastructure. The announcement in January sought to address this by saying Huawei would be excluded from “security critical” parts of 5G, but now it is expected that it will be phased out more generally. In a statement on Sunday, Huawei said the US sanctions were “not about security, but about market position” and that it wanted to find a way of managing them “so the UK can maintain its current lead in 5G”. The statement went on: “All our world-leading products and solutions use technology and components over which the UK government has strict oversight.” Last week the government was also urged to exclude Huawei by Lisa Nandy, the new shadow foreign secretary. In a significant toughening of Labour’s stance on the issue, she said the UK needed “far greater strategic independence from China, which means that we need to have home-grown alternatives for our 5G network and our nuclear power”. On Sunday Matt Hancock, the health secretary, was asked about reports saying the process of removing Huawei from the 5G network could start before the end of the year. He replied: “When we came out with an interim report on this earlier in the year, there were a number of conditions that needed to be met. “So I’m sure that the national security council will look at those conditions and make the right decision on this to make sure that we have both a very strong telecoms infrastructure, but also that it is secure.”