The head of MI5 has said he is confident that US intelligence sharing with the UK will not be jeopardised if Britain uses Huawei technology in future 5G mobile phone networks. A final decision on its inclusion is due shortly.

Andrew Parker said he had “no reason today to think that” the longstanding intelligence partnership would be affected – despite intensifying US lobbying against using the Chinese company in a critical piece of national infrastructure.

But the spy chief’s remarks comes as a US delegation – including officials from the National Security Agency – are due to visit the UK in a last-ditch attempt to persuade Britain to introduce a blanket ban.

A final decision on Huawei by British ministers has been repeatedly delayed after a decision taken in principle last spring to allow the Chinese firm to supply “non-core” parts of the high-speed 5G networks was leaked.

The decision was only taken by 5 votes to 4 in a closed National Security Council meeting, and the ensuing leak was blamed on then defence secretary Gavin Williamson, who was subsequently fired by then prime minister Theresa May.

Britain’s intelligence agencies have argued that any risks from Huawei can be managed, and the rare public comments from the head of domestic intelligence agencies will be interpreted as providing further support for Boris Johnson if he chooses to oppose Donald Trump on the issue.

Speaking to the Financial Times, Parker said that intelligence sharing between the US-UK was “very close and trusted”. He added: “It is, of course, of great importance to us. And, I dare say, to the US too, though that’s for them to say. It is a two-way street.”

But senior ministers such as Williamson have in the past been concerned about possible surveillance risks if Huawei technology is deployed. Some have been heavily lobbied by their counterparts in the US.

A final decision will also be seen as a crucial early signal in how far the UK wants to move towards the US orbit as trade talks with both Washington and Brussels loom after Britain formally leaves the EU at the end of January.

Last month, Johnson said at the Nato summit that he didn’t want the UK to be hostile to foreign investment – before suggesting that the impact on future intelligence sharing was critical to his final decision.

“On the other hand, we cannot prejudice our vital national security interests, nor can we prejudice our ability to cooperate with other Five Eyes [US, New Zealand Australia and Canada] security partners. That will be the key criterion that informs our decision about Huawei.”

Huawei has consistently denied that it has ever been asked by the Chinese government to introduce secret “back doors” into its technology, and has even offered to sign a “no spy agreement” with countries adopting it.

Its position is strengthened by the fact that Vodafone and other mobile companies say it is the cheapest and most advanced supplier of 5G equipment in the market, a point acknowledged by the head of MI5.

“Perhaps the thing that needs more focus and more discussion is how do we get to a future where there’s a wider range of competition and a wider range of sovereign choices than defaulting to a yes or no about Chinese technology,” Parker said.

The UK’s final decision is now expected in a few weeks.