Mobile phone customers could face signal blackouts lasting several days if network operators are forced to rapidly remove Huawei equipment, MPs have been told.

Executives from Vodafone and BT told the Science and Technology Select Committee they would need at least five years to completely remove the Chinese firm’s equipment without causing disruption.

The Government is currently reviewing a report from the National Cyber Security Centre (NCSC) and the potential security risk Huawei poses by being a part of 5G networks.

A Government decision in January permitted the Chinese firm limited access, but there is continued pressure to remove Huawei from communication networks entirely, and new US sanctions aimed at the firm’s supply chain has sparked a review of the decision.

Currently, Government policy permits Huawei to be in up to 35% of a 5G network, but as a “high-risk vendor”, it can not be present in the core parts of a network.

When asked about the impact of being told to completely remove Huawei equipment from their networks should Government policy change, both Vodafone and BT warned that it would cost “billions of pounds” and could lead to some customers losing phone signal for several days.

“Should the guidance become stricter it will have an effect, it will delay the rollout of our 5G, it will have cost implications and focus our investment in the removal of the existing equipment,” Andrea Dona, Vodafone UK’s head of networks said.

“If the current guidance were to be tightened and further restrictions were to be imposed, we would need to spend in the order of billions to change our current infrastructure.”

Mr Dona said it would be “highly disruptive” for customers if the Government asked the firm to remove Huawei within two years and any swap would see customers “lose their signal”, in some cases for “a couple of days”.

To avoid such a scenario, the Vodafone executive told MPs “a five-year transition plan” would be the minimum required.

BT’s chief technology and information officer, Howard Watson added: “It is logically impossible to get to zero (Huawei presence) in a three-year period.

“That would literally mean blackouts for customers on 4G and 2G, as well as 5G, throughout the country as we were to build that in. So we would definitely not recommend that we go down that route.”

Earlier in the session, Huawei defended its security record and denied that it would be compelled to follow any orders given to it by the Chinese government.

Huawei vice president Victor Zhang told MPs that it was independent of any government and it would always follow UK law.

Mr Zhang also urged the Government to give Huawei time to understand the implication of US sanctions before choosing to ban the company from digital infrastructure.

He called the sanctions “unjustified” and said allegations about security were not true, adding that Huawei believed it could still successfully operate in the UK in the short term.

“We have already submitted our initial assessment to our customers and to the NCSC and the initial solution is that in the short term there is Huawei’s capability to supply to the UK’s 5G and fibre solution, and we have already prepared for the next five years to make sure the UK’s existing network will not be impacted by the sanctions,” he said.

“We are working closely with our customers and partners to evaluate the long term impact – it takes time and currently we need to wait until the full details become clear from the sanctions, so we can come to a solution.”

Asked about any influence on the company from China, Huawei UK vice president Jeremy Thompson said employees were free to express views, just like those of other companies in the UK.

However, when asked by committee chairman Greg Clark if he could give his personal view on the new security law in Hong Kong, Mr Thompson said he did not have one.

“I am a telecoms executive. I have worked in telecoms all my life.

“My role is to enable our customers who are the carriers to provide communications faster and cheaper. I don’t have a view,” he said.

Mr Zhang added the firm was not in a position to comment on the political agenda and that while he would be willing to share a personal view, he would not do so in the public forum of the committee.