Boris Johnson has signalled that Chinese telecom giant Huawei will be blocked from accessing the UK’s 5G phone network because of American security fears.

In a significant shift in position, the prime minister appeared to bow to Donald Trump’s warning that the US could not share intelligence with any country that allowed Huawei to build parts of its critical infrastructure.

The firm has been the focus of huge controversy after Theresa May’s government refused to rule out using it to build “non-core” elements of Britain’s new 5G networks.

Trump, who has repeatedly insisted that the company is effectively an arm of the Chinese state and a spy and cyber threat, discussed the issue during a personal meeting with Johnson in Downing Street on Tuesday.

Although No.10 failed to mention the topic, the White House said that the two leaders discussed “the importance of both nations working together to ensure the security of our communications networks and guard against untrusted providers”.

The US has warned that it will break off high-level intelligence sharing with any of its “Five Eyes” partners – the UK, Australia, New Zealand and Canada – if they allow Huawei access to their communications networks.

Speaking after the Nato summit near Watford, Johnson was asked if he had told Trump that he had decided not to go ahead with Huawei.

He replied: “On Huawei and 5G, I don’t want this country to be unnecessarily hostile to investment from overseas.

“On the other hand, we cannot prejudice our vital national security interests, nor can we prejudice our ability to co-operate with other Five Eyes security partners, and that we will be how – that will be the key criterion that informs our decision about Huawei.”

Former defence secretary Gavin Williamson, who was sacked for leaking National Security Council conversations about the company, was brought back to the cabinet by Johnson this summer.

Although his personal security access within Whitehall has been downgraded, he is seen as a valuable ally of the PM.

Downing Street sources stressed that no decision had yet been made and that it was still subject to an internal Whitehall review, but the new government would have to make a decision quickly after the election.

It is understood that a key factor for the UK was Washington’s decision to include Huawei in its trade war with Beijing.

This summer, the US commerce department placed Huawei and 70 of its affiliates on its “Entity List”, effectively a blacklist that bars anyone on it from buying parts and components from US companies without government approval.

The UK’s National Cyber Security Centre, an offshoot of GCHQ, has previously stressed that allowing access to “non-core” elements of the 5G network would not compromise British security.

Huawei was seen by previous chancellor Philip Hammond as offering the best value for money, with only a handful of firms including Ericsson and Nokia, capable of providing the technology for the 5G work.

In its “declaration”, Nato said its member states would “need to rely on secure and resilient systems” of communication.

A Huawei spokesman told HuffPost UK: “We’re confident the UK government will continue to take an objective, evidence-based approach to cyber security.

“Our customers trust us because we supply the kind of secure, resilient systems called for by the Nato Declaration and will continue working with them to build innovative new networks.”

Johnson also insisted that China could be a “strategic partner” of Nato, and was not a “strategic enemy”.