Excluding Huawei from Britain’s 5G network will “significantly set back” the Government’s ambitions to extend broadband access, a former chairman of BT has warned.

Sir Mike Rake, who now acts as an adviser to the Chinese tech giant, hit out at what he said were “ill-informed assertions” about the dangers of allowing the company access to the UK’s critical national infrastructure.

His intervention comes as Prime Minister Boris Johnson faces the prospect of his first Commons rebellion since the general election over his decision to allow the firm to supply “non core” elements of the 5G network.

Twenty-six Tory backbenchers have signed an amendment tabled by former party leader Sir Iain Duncan Smith seeking to ban “high-risk vendors” like Huawei from the network after 2022.

The move has the backing of a number of prominent Conservative MPs, including former Cabinet ministers Damian Green and David Davis, Commons Foreign Affairs Committee chairman Tom Tugendhat and Tory backbench 1922 Committee chairman Sir Graham Brady.

It reflects widespread misgivings across the party over the decision, with fears that it could give China a “backdoor” to spy on the UK’s telecoms network.

However, in an open letter, Sir Mike said they should accept the advice of experts at GCHQ that the risks can be managed with the safeguards and limits the Government has established.

“Any attempt to further restrict Huawei 5G equipment, or to remove existing 4G equipment, will not only incur very significant costs, but prejudice trade relationships with China and will significantly set back the Government’s broadband ambitions,” he wrote.

“This in turn will further damage our competitiveness as an economy, at what is a critical moment.

“We cannot afford to set back the important technological and communication progress we have made, with ill-informed assertions which are not supported by the facts and the experts.

“The Government has taken an evidence-based decision and we should all support it.”

MPs will learn later on Tuesday whether the amendment to the Telecoms Infrastructure (Leasehold Property) Bill has been selected for debate.

However, supporters have played down the prospect of a Government defeat, saying the move is intended to “lay down a marker” ahead of other legislation later in the year to establish a comprehensive telecoms security regime.